FWIW, I am still having an issue with this, but mostly on iOS 26 and iPadOS 26, including on 26.2 26.1 [edit - typo].
Several things happen:
The system “Copy / Apple Intelligence / Find” button pops up and covers the Discourse “Quote / Edit / Copy” button - generally covering the “Quote” selection, which is always the one that I want to use.
There’s been quite a bit of discussion of various Safari issues on meta.discourse.org. I didn’t have time to read the entire thread to see if they’re talking about this one in particular.