There is a difference between breaking a rule for an obvious purpose or breaking a rule because you never exactly knew what the rule was.
There's where we part company. Nobody consciously knows the rules of grammar for a specific language, either native or acquired later. The only way to describe the grammar of a language is through observation of people speaking (or writing) it. If you find a situation where you find two conflicting rules, it's either because they are optional or because of a regional (or other kind of 'lect) difference.
Of the "rules" you find in the normative grammars, and style guides masquerading as same, most are not grammatical rules but style choices. (Here I'm thinking of the "use less adjectives" and "don't end sentences with a preposition" kinds of "rules".) Matters of spelling, punctuation, and usage have very little to do with the grammar of a language. (For me a grammar is a sort of abstract device for parsing and generating acceptable sentences in a given language.)
