!nick has unexpected behaviour when the target is already in use (!nick NickInUse ==> Nick changed from OldNick to NickInUse[m]1)

[Mikaela]

When user attempts to change their nickname with !nick to something that is already in use in the IRC network, there is no error message from the appservice, but instead my nick is changed weirdly.

For example:

0. I am @mikaela:privacytools.io or mikaela[m] at IRCnet.
1. I change my nick with !nick Mikaela
2. @ircnet:irc.snt.utwente.nl responds Nick changed from 'Mikaela[m]' to 'mikaela[m]1'.

In this case I happen to know that nick Mikaela is used by my ZNC, but I would still expect the appservice to tell me something like "The nickname Mikaela is already in use on irc.snt.utwente.nl" instead of changing my nickname to a third nick that I didn't ask it to do.

I have understood this issue to frequently cause confusion especially to users who don't have previous experience with IRC (which would tell Mikaela[m]10: Nickname is already in use. by the way) as the user would attempt to run the command again ("Nick changed from 'mikaela[m]1' to 'mikaela[m]2'." as now there is helpfully a fourth nick).