when is it artistically (or otherwise) defensible to break grammar

[© tweed]

I often mis-use tense, obviously capitalization, etc.  as a means of communicating.  where is the point at which breaking grammatical rules detracts from the message or essence?  is this readily identifiable or only to be applied on a means-tested, case-by-case basis?

[© tweed]

I've noticed that I've taken to using exclamation points (!) with more regularity