`data-uid` is not reliable at this point.  The key of the object/collection/hashmap in question here is actually not used elsewhere, except of the following logic:

The explicit key only exists to make the list of usernames unique; i.e., all users of an issue are collected and added to this object with a unique key per user.  If the same user appears multiple times, then it is only added once.

Uniqueness of DOM elements does not help here, because this logic reduces the DOM collection based on DOM element properties.