Screenshot from the RT site:
This enormous white space around the opening or closing single quote characters looks like some kind of a bug; but I couldn't find where the bug is. Doesn't seem to be anything wrong with the CSS; same white space appears in different browsers (checked with Chrome and Firefox); and it persists after I disable various fonts in browser dev tools.
The problematic characters are the "typographically proper" opening and closing single quote marks - i.e. ‘ or ’; but not '.
Very odd.
P.S.: and now, five to ten minutes later, this white space is gone. Huh.