It's a go to for dark market comms these days, but other than that, this is the first I've seen it mentioned on clear net.

I also didn't know it was closed-source and privately-owned in the U.S., which should have been a red flag for dark market users.

It's a red flag for many dark market users. When I see people offer their customer support on Wickr, I think "is this guy serious? everyone is really confident in this person?" and never contact anyone on Wickr.