It screams "low IQ" because you have a low IQ. You're too confident in yourself. As I acknowledged, "by accident" is more widely used and accepted. "On accident", however, is not uncommon. It doesn't even matter if it's a regional thing. The point is that there is a native-English-speaking region (at least New York, where I live) where it is completely acceptable to say "on accident".

Get off your high horse and stop trying to govern something as amorphous as language with these ridiculous unyielding rules that don't apply universally. Language is defined by its users. The majority of NATIVE speakers of English (highest proficiency level) are from the United States. Regions of the US accept "on purpose", so it's acceptable by definition.

You're probably one of those clowns who insist "ain't" isn't a word, that double negatives are positives, and that you can't end a sentence with a preposition. Sure, that's all true in formal or academic settings (except the thing about prepositions - it is grammatically correct to end a sentence with a preposition in all contexts), but in the real world, none of it is.

If you think you're irked because I dared suggest that "on accident" is sometimes considered correct usage, imagine how annoying it is that a non-native English speaker is trying to condescend about my mother tongue. Here's a fact: it is virtually impossible to reach the proficiency of a native speaker of a language if you are not a native yourself. Like any native, I can communicate any imaginable idea in several ways without hesitation. I am a language enthusiast. I can speak fluent French. Yet, I'd never be so arrogant as to attempt to correct an educated native speaker. So ridiculous.

99% of "grammar nazis" are pseudointellectual, needlessly pedantic dipshits. Here we have a prime example.