Why don't admins block the IP of the offenders?

We do block IP addresses all the time, every day.

However, unfortunately it is not as easy as you think to stop someone from coming back.
This is a common problem between every social network.

Blocking IP is the most basic thing we do, but users' IP changes regularly, and there are ways of "masking/hiding" them.
We usually do a lot more than just blocking IP.

When we are aware of an offender, we use multiple different methods of detecting and stopping them. This takes significant manual effort from us, but we do it all the time.

Unfortunately, we can't provide many details about what we do, as that would expose our security methods to the offenders, allowing them to use that knowledge against us, to continue offending. However, there is a lot of work done behind the scenes that our users don't see.

So, why do some troublesome users continue to come back?

Even though we successfully make their lives harder (when it comes to creating new accounts on SimilarWorlds), it is impossible to permanently, foolproof prevent someone from re-joining SW, if they are determined enough.
If they purchase a new device and move to another city, we can't really predict that.

Also, we need to be careful with how much data we track from our users, as we must comply with regulations such as GDPR.
While some users might like the idea of not being tracked, this makes it harder for us to ensure troublemakers are tracked and detected, which consequently makes it beneficial more for the troublemakers than the legit good users, in many cases.

However, what you should do is make us aware that this user has returned, so that we can use different methods to detect this user.

Why is a troublesome account still active, if admins are already aware of it?

In most of these cases, the user's account is fully limited, preventing the user from posting, replying or send any messages.
We do this for a number of reasons that we cannot disclose, as that would defeat the purpose of doing so, but we will eventually suspend the account.