Can confirm that you’re able to PRIVMSG channels you’re not on right now:
bash-4.3# telnet irc.twitch.tv 6667
Trying 199.9.249.252...
Connected to irc.twitch.tv.
Escape character is '^]'.
PASS {{nope}}
NICK btm_pl
:tmi.twitch.tv 001 btm_pl :Welcome, GLHF!
:tmi.twitch.tv 002 btm_pl :Your host is tmi.twitch.tv
:tmi.twitch.tv 003 btm_pl :This server is rather new
:tmi.twitch.tv 004 btm_pl :-
:tmi.twitch.tv 375 btm_pl :-
:tmi.twitch.tv 372 btm_pl :You are in a maze of twisty passages, all alike.
:tmi.twitch.tv 376 btm_pl :>
JOIN cereth
:btm_pl!btm_pl@btm_pl.tmi.twitch.tv JOIN cereth
:btm_pl.tmi.twitch.tv 353 btm_pl = cereth :btm_pl
:btm_pl.tmi.twitch.tv 366 btm_pl cereth :End of /NAMES list
PRIVMSG #cereth :cerHype
PRiVMSG #vortale :cerHype
PRIVMSG #elmagus :cerHype
PRIVMSG #night :cerHype
I’ve been present on #cereth with an IRC client and saw the message. Then I’ve opened a incognito Chrome and navigated to the 3 other channels - on none of which I’ve been via IRC, and saw the message on every oen of them.