Has anyone else noticed how arbitrary is the use of the definite article(the) and to a less extent capitalization sometimes?

Get a carbon monoxide detector.

This makes me appreciate the relatively consistent rules of capitalization in German. You just capitalize nouns, the beginning of sentences and in formal language second person pronouns (which imo is way more humble than capitalizing I in English).

Why do you post the same stuff under different titles in different communities? What’s the weirdest thing in english?