@ktv Oh dear, it appears Plume is case-sensitive for usernames, and our system lowercases them all to normalise them. This one will take a bit longer to fix.
@ktv Update - user fetching and mentioning should work now (easier fix than anticipated). Article URLs in search won't work yet as they're not "Notes" (toots/statuses), but "Articles", which is a different object we're working on support for.