Especially since it does actually post what I want to say, despite the error message, and it so far seems to be confined to that one message thread (no idea if it's just affecting me alone or anyone responding in that one.)

I just figured that's the kind of thing to bring up, in case it's helpful to know or evidence of some bigger problem lurking. Plus it lets people know that, if they're like me, they can respond in that thread despite the message.