This turned out to be a pervasive issue on Safari mobile, affecting:
- footnote popups
- AJAX previews
- control buttons that have popups
- category chooser on the Edit tab
- feed chooser on Promote tab
- admin panel menus (vBulletin)
- reputation controls (vBulletin)
- statistics popup in content lists
The problem is due to a number of quirks on Safari mobile:
- click events only occur on certain tags (such as A), rather than all tags. However, if CSS sets the cursor to a pointer on a specific DOM node, then exactly that DOM node is capable of a click event.
- the body tag is never capable of a click event.
- the above rules also apply to touch events.
It may take a few days to correct all occurrences of this issue in a way that does not generate conflicts between popups. In order to correct this issue, whenever a popup opens that requires a click-outside, mouse-leave, or touch-end to close the popup, every single DOM node on the page must be given "cursor: pointer" in order for the related events to trigger under Safari mobile.