It's probably a question of personality, custom and habit, but I tend to write like I speak (some would say "no, you speak like you write" :-) in any forum, including Slack, sometimes in defiance of the cultural norms of the audience.

It leads to something of a reputation for verbosity, but never the accusation of ambiguity or excessive terseness. I don't think anyone's ever said to me, "What did you mean by that two-word reply?"

It can be quite useful when replying to each point though, you can quote each one independently since they're not merged into one big blob of text.

Not saying it's impossible otherwise of course, just slightly more convenient.

I hope I never have to go back to using email for work.

Long messages for tickets, slack for near real time chat.

Email for transactional spam and emailing old friend once a year.