Suddenly the floating sky continent makes sense.
My god, that could be exploited to the extreme. I wonder when griefers are going to figure that one out.
Really seems to be a toss up what works and what doesn't without a server side install. Certain values (like those that dictate when and where you can build) seem to be client side, while others (like base count and weight) are strictly server side and can cause client side or even server wide issues. For example, weight mods may show you that you're not overburdened, but if it isn't installed on the server, you will constantly be snapped back into place to correct movement speed.
I'm fairly certain ones like the building mod can even skirt around Palguard, which is the current anticheat server owners can install. One particularly malicious one that can be used without Palguard (and I'm almost certain it could work with it enabled but haven't tested it) is this particular mod: More BaseCamp Levels
(Browser isn't letting me make hyperlinks atm)
If this mod is not installed on a server, but the user has it installed, it can be used to crash a server at will. Once you hit BaseCamp Lv 21 on an uninstalled server, you can can crash a server, AT WILL, doing the following:
-Attempting to make a new base, even if you have less than 3
-Attempting to add another player to the 21+ guild
I've learned most of this trying to figure out how to set up a balanced pvp server (protip: good fucking luck if you can't write mods yourself), and my word is it insane how easy it is to just install a mod and go buckwild. A group of 3-5 griefers could easily fuck up a bunch of the currently available Community servers in about 30 minutes each with like 10 minutes of installing mods and a bit of practice. It's kind of incredible how easy it is.