hides the spinbox controls (the arrows).
Not on Presto-based Opera it don't
Also, links to updated conversations always take you to the top of the page in Opera rather than to the most recently unseen post.
Finally, the fonts are kinda ugly in Opera on Debian Linux
"upload a file" link does nothing in Opera when clicked, and despite accepting a file from the Gnome file manager via DnD, doesn't actually upload it.
This is all using Opera Next:
User-Agent: Opera/9.80 (X11; Linux x86_64; Edition Next) Presto/2.12.388 Version/12.16
v12.16 build 1860
Everything apart from the fonts works fine in Opera Developer, which is their new one based on Chrome, so you probably don't want to fix the site for Presto-based Opera.