It’s weird – I think I used to notice homophone errors a lot more, but lately, not so much. And I find I make a lot more it’s/its/than/then/etc. errors than (ahem) I think I used to.
While it’s possible it’s just a result of a silent stroke or some kind of super early onset dementia, I think it also corresponded to shifting to a more fluid/easier-going personal writing process. Somehow I think maybe that meant using a more verbal/auditory portion of by brain, and the homophones started to blur together.
Things like sweat/sweet misspellings still leap out of the page like a slap in the face to me though, so I know what you mean.
(And while my ear doesn’t hear a difference between then/than, it does seem to depend on one’s dialect. People also make fun of how I pronounce ‘bagel’ even though I say it the exact same way they do, so YMMV.)
