Blocking a poster on pm’s

If it's a user name that hasn't been seen before, perhaps it's someone new who hasn't yet realised the aversion for private messaging that many people seem to feel. I used to belong to a couple of book discussion groups (many moons ago in the Dark Ages when everything happened by email) and it was perfectly normal to have private discussions with other members quite separately from the main thread discussions. I made some very good friends that way. But then trolling took off as a popular hobby among weirdos, so the practice seems to have died out. Maybe we have a new member who hasn't yet got the hang of the site. I wouldn't block anyone after only one private message (depending upon what it contained, of course!).

Open the message in "inbox".
There is a clear "block the sender button"

I’ve had a message too and couldn’t work out why. I’ve never seen the user name before and it was in response to a post that didn’t really need a private opinion.