Don't care about capital letter - word correction = capital letter sensitive?

when i write in a forum where i deactivated the capital letter check function and i write a word wrong, it gets red underlined. so far so good.

however, when i click on it in order to correct it, the suggested word is in capital letters. so the correction function “forgets” that it should correct the word without making a capital letter at the beginning of the corrected word.

is this bug known?