Hi.
I received a PM. I wrote a reply in the quick reply form. I hit submit.
The page reloaded, the message disappeared and was not sent. I was still logged in.
I've just tried this again. Same result.
I cannot reply to PMs. There is no indication this is so, and submitting a reply leads to it being silently wiped.
It's not clear which sub-forum to post about this, and this seemed most appropriate.
Using a recent Firefox on Linux, cookies on.