Related:
Pressing Enter in comment box unexpectedly submits form
Right now pressing Enter auto-submit comments and some other forms - but not others. When writing a technical answer you could need more than two lines of text f.ex. in a comment, and the good habit of pressing Enter to make a new paragraph comes into play... (and yes, currently paragraphs in comments aren't handled/rendered.)
Could you make it an option (ie. old/new behavior)? Right now it makes the Enter key a key to be afraid of, which isn't a good thing when you're composing text...
One alternative to option on/off could be to keep it on, but allowing the user to choose among a few key-combos (say, Enter, ctrl-Enter or alt-Enter) for the autosubmit function.