When I send tags on a server with the capabilities
labeled-response message-tags
, mIRC adds a label tag and also duplicates my own tags to a second tag token, breaking protocol.

I type:
/raw @+test=foo PRIVMSG #test :test

mIRC actually sends:
@+test=foo;label=0026 @+test=foo PRIVMSG #test :test

I'd really like mIRC to not fiddle in raw messages at all, but if the label really needs to stay, please at least remove the duplicate tags token so that it doesn't break the IRC protocol.