is it possible?
I don’t think that a user like you or I can block someone. If you indicated to a moderator that someone needed top be blocked and gave good reason, such as the offending person is violating a forum rule, then the moderator could block the person.
But just because someone doesn’t agree with your opinion, that doesn’t mean you can/should block them.
No its so I can prevent PM spam.
In that case, you should PM @DRow.
There’s a button to ignore threads, but that won’t help if the person is constantly starting new pm threads in which case you should do like puzzler7 said