To this day I always copy comments to the clipboard before submitting them or after I feel like I've put a lot of work into them -- owing to dubious browser UI[2] c. 2000, where e.g. you might accidentally lose focus of the text field, and then the backspace button would navigate backwards[1] and lose everything you had typed up.
So my muscle memory is a lot of ctrl-a, c.
[1] A mistake that Chrome adopted afterward and didn't reverse until 2016: https://tech.slashdot.org/story/16/05/19/2041232/google-chro...
[2] Wasn't the only cause, of course. The request could fail as well.