Hi, is there any way to add comments to replies in topics which are in "Q&A" category type?

That is too close to Threaded replies which this community is staunchly against in any form or fashion.

Flat replies have worked since 1991 and there will never ever be a need to upgrade from them. Ever.

Thoughts about improving on Flat threads will result in public floggings and other extrajudicial punishments.

Go do three Hail Mary's and repent from your sins. 😎