The test is screwed (and should really be a unit test, not a part of quotest) but the functionality seems to be working, as just tried in Quaternion.

This makes the account load fine, but it's not yet perfect: my test account with mxid @tobias/:matrix.org is shown as @tobias%2F:matrix.org.

(some other things are also broken, but I'd look at those in different issues / patches) actually those might just be symptoms of that problem, let's see

We could add unescaping in some other places; I'm just trying to stay conservative. Technically, it's possible to recover MXIDs even at the Settings level, by parsing the key and only (un)escaping only the piece that looks like an MXID - e.g., by using the fact that nobody's using : in key names so far, outside of the account names.

Looks like the Windows runner doesn't allow me to store settings in the registry?..