Did you disable the nodebb-plugin-markdown? This one is responsible for most text parsing including quotes (see this page for syntax).
No. Its enabled.
A problem is spotted in Firefox 52.7.4 32bit (Windows): user cannot use the post's dropdown menu:
On click the page is immediately scrolled to the top of the page.
Of course, I understand that asking to fix the issue for a browser of 2018 is too much, but I just want to be sure that that's because of the old browser and not the forum bug.
@aleksei if you want to make sure then try using a newer browser and see if it works
Works fine in latest firefox.