You may have as many as you like in your clan/group/base but don't roam or PvP (including base defence) with more than 3 at once.
Don't spam indestructible TCs in areas you don't intend to use. For example around another player's base to annoy them, or in remote spots to claim the area for later. They will be removed and you will receive temporary bans for repeat offences.
Our chat environment is generally quite pleasant but you can say whatever you like here. Steam's built-in chat filter is ON by default, so if you are able to see bad language it's because you have deliberately allowed it! You also have the in-game MUTE function.