Cheogram Android sends User Nickname https://xmpp.org/extensions/xep-0172.html along with all MUC presence, in a bid to show how we could do advanced nicknames that don't have to be the unique id / jid of the participant also.
In the special case that a user's selected nickname would result in an invalid JID (such as if it contains most emoji) the XEP-0172 element and the JID resource will necessarily differ. Cheogram Android uses punycode-encoded nickname as the resource in this case.
Since no MUC component currently supports enforcing room policies (such as no duplicate names or other anti spoofing policies a room may have) against XEP0172 in presence, Cheogram Android currently only honours/displays the XEP0172 element if it is exactly equal to the punycode-decoded JID resource.