The guidelines kind of understate the issue, when saying that
Discourse as a platform allows post editing.
…because Discourse as a platform heavily encourages post editing, and in fact will do its utmost to guilt trip you into editing a previous reply rather than posting multiple times in succession.
Which I’ve always felt is a misfeature, because it ignores the fact that other participants in the conversation may be reading replies, or even replying themselves, using the email interface. Email users only get the first version of a reply, not any subsequent edits.
So, if I post in an ongoing discussion, then substantially edit that post after-the-fact, there’s a significant danger that a previous participant, following the discussion only via emailed reply notifications, ends up responding to the original version of my message rather than the edited one.
In GitHub Issues (another platform that supports full email-only participation), if I have to significantly correct some post I’ve written, I’ll first post a new reply with the correction, then edit it into my previous reply and delete the update. That generates an email notification of the update to email users, without cluttering the website version of the conversation.
(On Discourse if you post twice in a row, it will do that for you, forcibly joining your two replies together into a single one. I’m fine with that, I suppose, as long as it still generates email notifications for both posts.)
Anyway, I was wondering if it wouldn’t be worth touching on that — far more succinctly than I have here — in the Content Editing section of the Guidelines, as a reason (one of several) why users should avoid making substantial edits to replies in ongoing conversations, in particular. The potential badness of even immediately editing an existing post increases with the length of the preceding discussion and the number of participants (== potential email followers).