I assigned this to Lewis, although it's up to him who to assign this to. Also, I've never used Phabricator before now, so this could be the wrong place altogether.
While working on a post to Jack, I noticed that Monaco wasn't displaying right.
The Hubs menu ("MORE WIKIS") and the user menu ("MORE") are broken. I believe they are supposed to drop down on either hover or click, but regardless of whichever one you do, nothing shows.
This is a usability issue. The user "MORE" menu has access to preferences, and wikis using Monaco could drive users away because they don't know that Preferences can be found in Special:SpecialPages. This is where e-mail, password changes etc. are done, so I will say that access to Preferences is mission critical. Also note in other themes Preferences are up there as well.
I'm not at a desk for about six days, but I will be on mobile.