It appears that I forgot to add the ".key" after the $msgtags(subscriber) part. I have indeed just tested this script in a friends channel who is a partnered streamer and it works 100%. The !addme command will ignore anyone who is not a subscriber of the channel.

I am using the latest version of mIRC as well as SReject's JSON and mTwitch scripts (Core and DisplayName). They are worth adding to any mIRC bot for Twitch IMO. If that isn't an option for you, I believe that at the very least, you will need your mIRC to request "tags" from the Twitch server. Make sure that you have something like the following code in a script file or in your remote.ini file. If you have a mIRC bot on Twitch, chances are that you may have already added the "commands" and/or "membership" to be requested, but not the "tags."

Code:
ON *:CONNECT: IF ($server == tmi.twitch.tv) CAP REQ :twitch.tv/commands twitch.tv/tags twitch.tv/membership



I fixed the earlier script here:
Code:
ON *:TEXT:!addme:#: {
  IF (($msgtags(subscriber).key) && (!$istok(%sub_list,$nick $+ $chr(44),32))) {
    SET %sub_list %sub_list $nick $+ $chr(44)
    MSG $chan $nick $+ , you have been added to the !list.
  }
}

ON *:TEXT:!removeme:#: {
  IF ($istok(%sub_list,$nick $+ $chr(44),32)) {
    SET %sub_list $remtok(%sub_list,$nick $+ $chr(44),0,32)
    MSG $chan $nick $+ , you have been removed from the !list.
  }
}

ON *:TEXT:!list:#: MSG $chan $left(%sub_list,-1)

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