It was suggested that some examples be given as to what is deemed abuse so that people have somewhat of an idea here. However, please note that this is not a complete list (that could potentially take too long, plus it's quite possible that we've yet to encounter something and thus it might not be possible to list it until such a time occurs). That said, here are the more commonplace and major examples of abuse:
1) A member/person is a known male. For some reason, said member/person creates an alt account that is a female persona and doesn't let anyone no about this super secret alt account. Using this female persona account, they specifically target members who have explicit rules in their Request Threads stating that they are uncomfortable RPing with male members. They lie to these members and pretend that they truly are female just so that they can RP with these people for some unknown reason. THIS IS ABUSIVE AND A VIOLATION OF SOMEONE'S RIGHTS! (This can go for females pretending to be males or just about anything... but the idea is one in the same).
2) A member/person has an account where they are decently known by members and/or staff (not to mention visible on the boards and in chat) and then create an alt account and try to dupe members and/or staff into believing that the alt is truly a unique individual. It is made worse if the original account has a track record of some sort while the alt, technically, does not.
3) A member/person creates more accounts than the allotted five. As it is, five is WAY more than enough. In all honesty, people really shouldn't need more than ONE. However, in wanting to keep an open mind and thus allowing the ability for people to explore creative freedom, people are granted the privilege of up to five. So, by purposefully exceeding, you are abusing that privilege. By ignoring staff when called out on this, you are abusing it even more so.
Anyway, these are probably the most common offenses that have occurred and they can be pretty serious depending on the situations--especially the first one that was listed and even the second one. But hopefully this lets people see and understand the potential seriousness of the issue and why clarifications are being made.
Thanks.