Just a heads-up for Youtube users: if you find yourself unable to post a comment on a video and instead just get a message that says "Error, try again", then check if you've used the term "http" (or possibly "https") in your comment. Doing so is enough to trigger Youtube's "no URLs in comments" rule, even when it's not actually part of a URL.
Needless to say, this is really rather braindead. Specifically:
- There is no informative or otherwise useful error message; in fact, the message given is actively misleading insofar as that it makes it appear as if there is an intermittent problem accepting the comment on Youtube's side.
- The term "http" cannot be used even when it's not part of a URL.
- Actual URLs can still be posted (and regularly are) if you break them up by inserting some whitespace here and there.
In other words, the rule applied to would-be comments that tries to keep you from posting URLs a) fails to do that, b) interferes with comments that do not contain URLs, and c) fails to inform and in fact misleads the user about what the problem is if posting a comment doesn't work.
It took me a while to figure this out, so if you ever have this problem... here's your solution.