Ok purplekaykay, I looked into what you told me, and the player who supposedly created and placed the signs, hasn't been on for a while. More than 3 weeks.
When I checked who actually placed the signs, this is what I got, see spoilers for details:
Going by the above spoilers, even if those signs were placed by the player who you said placed them, that is his base area.
The content on the signs, didn't really violate any rules of the server either.
However, even if he was the one who actually placed the signs in question, that is his base area, he has signs that I clearly seen notifying that the area is his.
My advice to you would be: keep your sister off of your account.
She actually did violate a couple server rules. I will let this go as a warning this time, but if she gets on your account again, and does stuff under your name, that does violate the server rules, the course of action taken will be different.
EDIT: PurpleKayKay, you have been banned for stealing from another player. Stealing is not tolerated here.
I wish you luck on finding a server that is best for you.
Right. The server is running Minecraft version 1.8.8
In your opinion, that may be the "wrong 1.8".
In any event, it won't matter to you anymore. The amount of theft you did caused you to get a permanent ban, that can't be appealed.
However, everything you stole, or your sister stole, was able to be recovered, so no real loss.
We have very detailed tools to help us pin-point things before I make a final decision, which was final a few days ago.
I wish you luck on finding a server that better suits your needs. -Ramp