It is a little bit painful to read. Capital letters exist for a reason (to make reading easier)

what exactly do capital letters make easier to read? i dont think readability is why they are used for proper nouns, names, nor the pronoun I. and obviously ALL CAPS isnt a readbility improvement either. presumably just as delineation of one sentence to the next? (forgive my ironic non-use of caps to start sentences haha).

Correct. The dileneation of one sentence to the next, which is somewhat an indicator of the end of one thought - or fragment of thought - and the beginning of the next.

Look how nicely davetron5000's comment below can be read. Proper capitalization makes text much more readable.

capital letters are atypical in many internet circles, particularly younger. so maybe it's a habit from frequenting those circles or a deliberate branding choice

Well I'm not that young. I guess it just helps me to write fast when I'm not thinking about punctuation/grammar. I'll make more effort to capitalize.