This is a bit technical, but there’s a little-known feature on Mastodon called “Authorized Fetch”, aka “Secure Mode”. By default it is switched off as it uses more resources and can cause compatibility problems with servers running older software.
However, if it is switched on it makes user blocks more effective, as it makes it harder for blocked people on other servers to interact with public posts from people who blocked them. (It only really helps with public posts, private posts are already protected against trolls.)
It can only be activated by your server’s administrator. It might be worth asking them if they have Authorized Fetch switched on in order to better protect their users. There’s a technical description of Authorized Fetch here ⧉ which they might find useful.
Authorized Fetch cannot be switched on from the graphical interface, it requires manually editing a certain file on the server. If a server is on a managed hosting service, the server admin can ask the managed hosting company to switch it on for them.