This has been declined several times 1 2 3 4 with two related arguments:
- Comments have little content so little is lost, anything significant should be an edit or an answer instead.
- Comments are not important, so the system shouldn't make them easier to use.
The problem with this argument is that they apply to chatty comments, but that's not all that comments are about. I've been hit several times by this while composing moderation-related comments (both as a diamond moderator and as a user guiding other users). I try to give tailored guidance to users, so I might write a comment like this:
Welcome to Foo Bar Stack Exchange. This is a [questions and answers site](http://foobar.stackexchange.com/tour), not a discussion forum. We've found that [questions about … ](http://meta.foobar.stackexchange.com/questions/98/should-we-have-a-policy-about-questions-about-ellipsis) invariably lead to extended discussion and exchanges of opinion rather than useful advice, which [does not fit in our Q&A format](http://foobar.stackexchange.com/help/dont-ask), so I am voting to close this question. You're welcome to drop in to our [chat room](
*#*(\&\@\T#\%\&\^#( accidentally left-clicked instead of middle-clicked to find the link to the chat room.
Now I can retype this. Or I can just cast a close vote and not offer any guidance.
There are comments with real content, that take several minutes to write. Not all comments are trivial, and these non-trivial comments are the most important ones. Making comments so easy to lose is an incentive to not leaving any constructive guidance — leave a form comment or none at all. It would make sense if the system was geared against form comments, but it's actually geared towards them since specific comments are so brittle to compose.
Please arrange for the system not to hinder constructive comments. Either save the unfinished comment somewhere and recall it on page load, or arrange for the browser to do that (it should work both when clicking on a link and when closing the tab — I wrote this answer after accidentally closing the wrong tab while composing a comment a bit like the one above). Or alternatively display a confirmation warning when navigating out of the page.
I prefer saving and restoring the comment to a navigation warning, because transparent save/restore is seamless and isn't in my way if I just decide to abandon the page. Ideally the comment would be saved on the server side so I can start composing a comment on one machine and finish it on another, but that would be icing on the cake. I can see the advantage to a navigation warning as well — it alerts me that I might have forgotten to send a comment, and if I want to cancel that comment, it's very easy to delete the text from the entry box. But either way, don't make me lose work because of one misclick during normal workflow.