They rent their servers, so it depends on what you consider as running the server. They have virtual access to it, but they don’t own the hardware. At least, that’s the case for countries I checked, maybe they have their own servers somewhere too.
Such as? I’ve been looking to buy one recently. Are there any you could recommend for an amateur that wants to host totally random small services on a microcomputer?
Delete all data from the previous account and make a new one. Report the troll to moderators. Consider never visiting that place again if the mods won’t help you with the harassment.
If the troll doesn’t have access to the forum’s server, then all you have to do is learn some opsec and be aware of what you share with strangers on the Internet.
If the troll does have access to the server and you absolutely need to visit the forum (which I’d advise not to in such a case), then in addition to what has been said above, use VPN with a hardened browser or Tor to access the forum.