I think the best way to handle this problem would be to automatically remove them at the time of posting, or replace double quotes (") with single quotes (').

But this would mean a change of the code for creating threads and posting to threads which I can't do, and I don't want to burden someone else with it...

It does not help to replace the " with " because when someone copy-pastes the result they will have " in the copied text, not ".

cu, Andreas