Update: This error seems to have been resolved. Some of the steps shown below are therefore not necessary unless if you’re still experiencing the issue.
If this is not your first time reading this blog, then you might have realized it has a YouTube Channel of the same name. It’s actually the inspiration behind this blog itself. But that’s beside the point.
What am getting at is a mysterious problem I’ve encountered of late while interacting with the channel. The problem: every time I try to make a comment or even reply to one, I get the following error: Comment failed to post.

Now, I only realized this after trying to reply to a comment on this video. My set-up is a desktop running Windows 7 32-bit and Mozilla Firefox (v45.0.1) was the browser I was using at the time. Noting the urgency of the reply, I decide to get down to the bottom of this error as quick as possible.
Troubleshooting Comment Failed to Post
The video below shows you a demo of the error:
My troubleshooting went down as follows:
- Disable Add-ons
My first instinct was to disable add-ons seeing I use quite a number of them. So I restarted Firefox in safe mode and tried replying. It failed with the same error. - Make a New Comment
Tried making a new comment on the same video instead of replying, and it failed likewise. - Clear Web Cache, Cookies and Passwords
Wiped the browser clean using CCleaner and restarted the browser. Still failed. - Update Firefox
I updated Firefox to the latest version (back then it was 49.0.1) and it still failed. - Use Different Profile
Used a “fresh” Firefox profile on a different account, and it still failed. - Try different Browser
I was getting rather impatient, so I decided to test Chrome which am not a big fan of. I logged in as usual and tried replying. Surprisingly, it worked this time. So what this was telling me is that the problem was the browser and not YouTube. Somehow I wasn’t convinced and decided to go back to Firefox to resolve the issue. After all, I had invested so much time on it, you know with the extensions and bookmarks. - Try Commenting on a different Video
So I went back to Firefox and commented on a different video this time round. Surprisingly it worked. Just to make sure, I tried commenting on the initial video, and again it failed.
Now this was just confusing. Does that mean it’s the video that’s the problem? Seems unlikely seeing with Chrome it did just fine. Or was there something special about this particular video? Maybe, just maybe.
One by one I started commenting on all the videos in the channel and for the most part they all worked until this one failed with the same error. A quick comparison between this video and the initial one revealed something — they both featured a Highlighted Comment at the top.
What are Highlighted Comments?
(Update: A more detailed and conclusive explanation on what Highlighted Comments are can be read here or watched here.)
That’s the exact question I asked myself because up until this time I had never encountered them. So I googled it and got nothing concrete.
The first noteworthy result that pops up is a post from YouTube’s official blog that dates back to 2010. It doesn’t explicitly mention highlighted comments instead it talks about highlight views and ratings improvements on the video page.
The second noteworthy result is a video from ElitheComputerGuy. In the video which dates back to Jan 2015, Eli says the highlighted comments is a new feature which highlights comments from YouTubers with a lot of subscribers (his being 450K).
A quick look at my commenter’s channel destroys this premise. However, it was the first comment so maybe that counts.
More recent results, especially on Google’s Product Forum seem to indicate that the highlighted comments is a replacement for the old Linked Comments.
Other results indicate that they’re either comments that have received a lot of attention (likes, replies) or that have been flagged by the uploader. Simply put, there’s no consensus on what they’re. Google ought to settle this once and for all.
The Solution
From what I’ve figured after further tests, Highlighted Comments, at least in the point of view of the uploader, are comments that are highlighted for convenience – to get your attention for an action so to speak. Why do I say that?
If I open the video directly (instead of replying from the comment section in the video dashboard or from the email comment alert) there’s no “Highlighted Comment”. Commenting this way works with Firefox. Chrome works both ways.
Why Firefox fails to comment with Highlighted Comments on remains a mystery to me. Could be my system or a Firefox bug, seeing rusty Internet Explorer 9 works just fine.
UPDATE: Fix For Comment Failed to Post
After getting some comments here and on my channel about Chrome showing similar symptoms, I think it’s now safe to conclude that this is most definitely a YouTube Bug. To get past this issue when commenting or replying, you need to make sure the Highlighted Comment label is not showing.
To do that, load the video this way: In the Address bar, edit the URL to remove the added part (parameter).
For example, for the video: https://www.youtube.com/watch?v=fo5h411G5Sk&lc=z12rhv1yatubiprsw23hwvkzxxvtd1mlm
, the actual video URL is: https://www.youtube.com/watch?v=fo5h411G5Sk
All you have to do is remove the part starting at the ampersand (&). Opening the video without the added parameter won’t show the Highlighted Comment label, and so your comment should work.
Alternatively, if you’re the video uploader, you can open the video directly from My Videos page in your YouTube Dashboard.
It happens for me too, in every web browser, when replying via the "Highlighted Comment" option in an email link (i.e. Youtube sends me an email notification telling me a reply to one of my comments has been posted. So I click on the "Reply" button/link in the body of the email, and it takes me directly to the comment via a URL switch/parameter – That's what a "Highlighted Comment" is.)
When I remove the parameter from the URL and find the comment manually, I can post with no problem. This is directly related to the URL switch functionality, and the bug is in scripting running on Youtube's frontend. It all started around the beginning of the year for me, and is a consistent bug in every browser made.
Before this one, there was another bug on youtube wherein certain punctuation characters (like the " or ' symbols, for instance) would be replaced with a hexidecimal ASCII code for the symbol in the text of the comment whenever you tried to edit a comment that you'd posted. This went on for years before someone at Youtube finally gave enough of a sh!t to fix it. Let's hope this bug doesn't take as long or longer for them to get off their azzes and fix!
NOTE TO YOUTUBE: FIX YOUR SOFTWARE BUGS!!!
Hey Steve, thanks for clearing up the technical bits on the issue. I've also been getting comments on a Youtube video demo I did on this issue about Chrome giving the same results however when I did my tests back then, Chrome used to work for some reason (even with the parameter). Later on though it did fail at times. So at this point I think we can safely conclude that it's not a browser issue but a Youtube bug. Let's hope they'll fix it ASAP. Thanks again, I'll update the post accordingly.
It happens for me too, in every web browser, when replying via the "Highlighted Comment" option in an email link (i.e. Youtube sends me an email notification telling me a reply to one of my comments has been posted. So I click on the "Reply" button/link in the body of the email, and it takes me directly to the comment via a URL switch/parameter – That's what a "Highlighted Comment" is.)
When I remove the parameter from the URL and find the comment manually, I can post with no problem. This is directly related to the URL switch functionality, and the bug is in scripting running on Youtube's frontend. It all started around the beginning of the year for me, and is a consistent bug in every browser made.
Before this one, there was another bug on youtube wherein certain punctuation characters (like the " or ' symbols, for instance) would be replaced with a hexidecimal ASCII code for the symbol in the text of the comment whenever you tried to edit a comment that you'd posted. This went on for years before someone at Youtube finally gave enough of a sh!t to fix it. Let's hope this bug doesn't take as long or longer for them to get off their azzes and fix!
NOTE TO YOUTUBE: FIX YOUR SOFTWARE BUGS!!!
Thank you, you are right, i've finally found the answer!!!
Nope. There seems to be some people you can't reply to. I've been on several channels and videos where I can reply to everyone else's comment except one person. I don't know how they do it. Maybe special settings in their account?
What you're experiencing is probably unrelated to this "bug" which Google seems to have long fixed. Regarding your issue, maybe that user has blocked you as Google points out here: https://support.google.com/youtube/answer/56113