Tags for this video have been changed from 'parasite, behaviour, host, hairworm, yuuuuuuuck' to 'parasite, behaviour, host, hairworm, Gordian worm, tapeworm, xenomorph, bug hunt' - edited by my15minutes

A simple solution to your bug hunt (1, 2 & 4): use a W3C standards supported browser (such as FireFox!) The 3rd is a problem known to the Sift Lords (I've reported the same thing a couple of times) - although I'm not sure how exactly it happens...

I agree that a more definitive list of allowed HTML would be useful (I'm always finding more tags that are supported, such as Ordered Lists: like you found). The "(Basic HTML enabled)" is a reminder of the select HTML enabled when commenting, which links to the following (in the Sift FAQ):

13. What HTML tags are allowed in comments?

The following list of tags are supported in your comments. In addition, any normal URL (beginning with "http://") that you type will be converted into a hyperlink automatically and any newlines will persist.

a, br, blockquote, b, strong, i, u, s, strike, em, small, sub, sup, code, kbd, tt

Tried it. Still empty. I have to get some sleep now. If needs be, discard the video if it interferes with your bug hunting.