Nick abuse kind of depends based on the moderator. I have no issue with that, although messages might be harder to send to you. Nick abuse is only bannable if your nickname is highly racist, has language, or is otherwise offensive to moderators and players.
Mudkip is fine. As long s you are not impersonating another player or famous person, you will be fine. So don't go naming yourself CaptainSparklez or PewDiePie. Has your question been answered?
There's a link in my signature which should hopefully explain things a little better. But basically, no, this instance wouldn't be considered nick abuse unless someone with the MC name of "Mudkip" joined Skyblock and objected.
Okay, your question has been answered. I am going to lock this now. If you want it unlocked, feel free to message me or another staff member. Kind regards, Bdark.