I’m noting quite a few more double posts in comments recently, which probably has something to do with the fact that in the last week or so it seems like the comments pop-up is taking more time to upload the comment — and in some cases may not give an indication the comment has been uploaded at all. I don’t know why this is happening, but I’ll see if I can figure it out.
In the meantime: If you’ve commented but aren’t given any indication that the comment has uploaded after a reasonable amount of time, do this before you press the “post” button again: Reload the main Whatever page to see if the number of comments on the entry has gone up by one or click on the timestamp for the entry to go to the archived page, which has all the comments following, including (hopefully) the one you just added.
If you don’t see evidence of your post going through, go ahead and hit post again, of course.
Also, if you do accidentally doublepost, don’t feel you have to add in an additional post apologizing for the double post. I assume they’re accidental and won’t hold them against you, much.