I see two comments of Robin Chapman on the answer Kernel of the tangent map split into many more comments. Am I the only one to see this? Thanks for checking.
Another problem with this "feature" is that comments are posted while still being edited.
This leads to problems when other users quickly comment on the half-baked comment, causing awkward out-of-sequence effects in the comment threads as replies address the half-baked material, which is then deleted or edited or reposted in version 2.0 after the comments discussing it have already appeared. These time machine causality effects make some of the comment threads hard to understand for readers not involved in the exchange of remarks.
A genuine click on the POST THIS COMMENT button should be required before comments are broadcast.
There has already been feedback against this new "feature" whereby Pressing Enter in comment box unexpectedly submits form. Despite many comments there showing how this "feature" is undesirable, there is no reply at all from the Stack Exchange people, and the latest edit by Jeff Atwood on the question here shows it's not as if they're unaware of this either. Chalk this up as another instance of Jeff Atwood autocracy, I guess. I find this annoying as well, and don't know what to do. :-)
It is likely because Robin pressed Enter which causes the comment to be submitted. I have merged the comments manually.
I blame me. OK, I didn't make the actual code changes, but I did hint more than a few times that enter could submit comments.
Either way, Jeff is aware that it is causing problems so maybe the old behaviour will revert before too long. In the interim, I suggest (to borrow a meme from "chat"):