Learn Turkish: En alaycı yorumları duymazlıktan gelecek kadar umursamaz davranıyor. - He acts indifferent enough to pretend not to hear the most mocking comments.

It combines the verb root duy- (hear), the negative aorist -maz, the noun-forming suffix -lık, and the ablative -tan (from), followed by gelmek (to come). Literally, it translates as 'to come from a state of not hearing.' This is the target formula for pretending you didn't do or experience something.

Why does the sentence use the future form gelecek before kadar?

To express doing something 'enough to [action]' or 'to the point that one will [action]', Turkish often uses the future participle -(y)ecek followed by kadar. Here, duymazlıktan gelecek kadar means 'to the point that he will pretend not to hear.'

Does umursamaz use the same negative suffix as duymazlıktan?

Yes, it uses the exact same negative aorist suffix -maz. It comes from the verb umursamak (to care or mind). While in the first phrase the suffix helps form an abstract noun (duymazlık), here it creates an adjective meaning 'indifferent' (literally, 'one who does not care').

Why is yorumları (the comments) in the specific accusative case?