MATLAB is not doing anything of the sort. In fact, that is not a response from MATLAB at all, but from the web site, from MATLAB Central.
The website is telling you that you cannot post a comment to that page at that time, because the page has changed in some fundamental way. Sometimes it may be that the post was actully deleted. But in some way, something has changed.
What I would suggest you do is to copy the entire comment you were going to make. Now it resides in the temporary copy/paste memory of your computer, so it can be pasted back in when that is appropriate.
Next, RELOAD the page. See what has changed about the post where you were going to post this comment. Often you will find, as I said, that the post was in fact deleted. I often see that happen, and I realize the person who made the post realized what the problem was, and they just deleted their post. Sometimes it was just that the person made some significant shange to their post, perhaps adding information to their question, etc.
However, if after reloading the page, you still find the post there, but with some changes made, now you can simply post your comment. No problem.
