What's the etiquette here? Is it preferable for me to delete the above message, which shows the original off-topic/spam message?

Yeah, I'd say that's probably for the best. Maybe replace it with just [SPAM POST DELETED] or something.

Looks like I can only delete the thing. Editing text still keeps the shared spam msg. I'll do that ig.

(I cleaned up some other stuff -- thanks for reporting this stuff folks!)