UserID type not used consistently

[gewitternacht]

Link to problem area:
exemplary https://spec.matrix.org/v1.18/client-server-api/#molmv1curve25519-aes-sha2

Issue
Sometimes, the type of fields that are supposed to contain user IDs is given as string, and sometimes as User ID, with a link to https://spec.matrix.org/v1.18/appendices/#user-identifiers.
In the example above, this is especially noticeable, as it is the case for two fields right next to each other, but the issue persists throughout the spec.

This is confusing – is the use of different types intentional, and if so, what's the reason?
Otherwise, all user ID fields should probably have type User ID.

[richvdh]

It's historical rather than intentional; converting to User ID (likewise Room ID, Room Alias, etc etc) is a work in progress. See #2359 and #2358 for some recent work in this area.

[richvdh]

(as a side note, links to specific versions of the spec are preferred over /latest, because (a) the fragment IDs go state sometimes, (b) it's often easier to understand bug reports in the context of the spec at the time the bug was reported. I've updated the link in your report.)