As @jonathanstea.bsky.social points out here, a strong predictor of trolling is the tendency to derive pleasure or enjoyment from being cruel or demeaning to others. By blocking, it deprives them of that pleasure.
From the comments I receive (see below for just a small sample from last week), you can see how this could plausibly be the case - many of whom are then shocked and indignant to be blocked.
"It is important to remember that respectful disagreement is not trolling — and in fact, voluntary engagement in uncomfortable conversations is necessary for growth intrapersonally, interpersonally, and socially."
These conversations don't often seem to work in this medium.