So, in a DM, the indicator on the right normally reads 'unread' or 'last read' or whatever. But in a certain chat, it just says 'unknown'. Have they deleted their account, blocked me, or something like that?
Yeaaah, it's been DAYS now with no response. I can understand privacy - everyone needs it from time to time. But when they've written an introductory post and then I respond, they just... bolted, I guess.
Don't put faith in that indicator; it's meaningless, and I've figured so since pretty much day one here. Instead consider site activity in general from the user, issue a reminder, wait for a bit and then make a judgement depending on their response (or not) vs what they're otherwise doing.