We did have a good reason for attempting to turn it off originally, Chrome was trying to autofill people’s personal information (like their address) into the composer, and that was a little alarming: New post/reply sometimes tries to autocomplete my address on Chrome
It’s unfortunate that some Android keyboards seem to use autofill to disable a keyboard’s predictive text, that’s really not the correct use of autocomplete="off" at all according to the HTML spec, and it conflicts with Chrome’s (also incorrect) usage of autocomplete.
Does your keyboard work as expected on this test form? https://codepen.io/wavyknife/full/JjBVxMM
The inputs on that test form have autocomplete="discourse" which might be good enough to disable Chrome’s overzealous autocomplete without disabling it in other situations.