Hmm, indeed, it seems that DBD::Pg handles question marks in comments correctly now (3.16.0).

I distinctly remember that this used to be a problem a few years ago.

But you're right about the operator-with-questionmark case: there is actually a "?" operator in postgres (to test for a key in a jsonb object), and you have to escape it if you want to use it in a query with DBD::Pg (which makes the SQL incompatible if you want to reuse it with e.g. raw psql or Go/sqlc).