Backspace deletes an entire Thai character instead of just the tone/vowel mark on top

Steps to reproduce:

1. Type Thai text with a tone mark or vowel mark on top of a consonant, e.g. type "สวัสดี"
2. Place cursor at the end of the text
3. Press backspace/delete once

Expected:

Only the last mark (ี) is removed, leaving "สวัสด"

Actual:

Both the mark and the consonant underneath it are removed at once, leaving "สวัส"

This happens because in Thai, tone marks and vowel marks are separate characters that are visually stacked on top of consonants, but they should be deletable independently with backspace. Capacities appears to treat the consonant + mark as one unit and deletes both together.

Platforms affected:

Mac app, iOS app, and web app — all show this behavior.

Not affected:

Other apps handle this correctly, deleting one character/mark at a time.

Impact:

Thai text uses tone marks and vowel marks very frequently, so this makes correcting typos slow and frustrating, since fixing one small mistake often requires retyping several characters.