I don't think blocking can work unless it's done by moderators, otherwise these trolls would still be able to create posts anyway.
In addition, there are many cases where members were banned from the forum, but these troublemakers immediately created new accounts and returned to the forum under different names.
I don't think you got what OP was trying to suggest
He wants a feature where you can block any troll, and he won't be able to see your past and future posts, he won't be able to reply to your past a future threads etc. Right now what we have is just an ignore button
Of course someone can create a new account and continue trolling but then you can also block him buy a click of one button and so on.
Where i think this feature will have some trouble will be when it comes to the trust system. Most especially the trust feedback and flags.
1. Scammer scams me, and then he blocks me before I tag or create a flag on his profile.
2. Malicious person leaves false feedback on my profile and then he blocks me