Nitpick: on skim, `contextMenuDisallowed` suggests to me that the context menu is, well, disallowed, whereas in the details this is really only `contextMenuDisallowedOnSafari`.  I'm not sure what to do with that thought -- thinking it, rolling eyes, and just moving on is a fine option.  But maybe it gets to just what this class is meant to flag.

Thought: should the context-menu-disallowing behavior actually be applied to the `dl-clickable` class?  That is, what we're saying about this element is that it's a click-for-download element, and then what we're saying in the JavaScript is that, hey, Safari is screwed up for *all* click-to-download (`dl-clickable`) elements.  It's not so much a characteristic of this element that it's context-menu-disallowed as it's a characteristic of this element that it's a `dl-clickable` and it's a characteristic of Safari, expressed in that event handler on line ~142, that there's special handling of context menu invocation needed for Safari consumption of click-to-download elements, namely, suppress the menu in that context.