Content being removed is a different matter. Claiming that you are being censored by limiting the number of characters you can use is different.
Whatever your instance's reason for removing your posts, that's their decision. It's their instance. But there is currently no setting to limit the number of post characters of individual accounts.
If clarifying it is offensive, then my apologies. My only intention was to explain that such a feature doesn't exist currently, maybe one day it will.