You should add a edit button when you comment on a members thread, there a times where I accidentally do grammar error or a mistake on a post and i'm not able to edit the post, unless it's your own thread.
Yeah that's only for threads you've created. (the picture link) For example there is a thread a member has created, and I didn't proof read what i've posted, there wasn't a edit button to fix it. Gyazo - 339384ae9d51d0057c4d9f867be3f49c.png