I agree with Sam that this needs to be based on actual problems within a community rather than guessing what the problems may be.
And sometimes the detection is hard – for example we say in the FAQ that people should not end posts with signatures, such as:
Hello, how do I make a post in Discourse?
Thanks in advance,
John Q Public, Esquire
http://example.com
How do we reliably detect a signature at the bottom of a reply? How do you reliably detect curse words without creating false positives? There is a limit to what you can automatically process here.
We do enforce a number of fairly narrow, specific rules around topic titles based on noise characters, length, entropy, and so forth – for example, I see topics here that end in multiple question marks, but we should not allow that.