In your example there, twitchnotify already does proper capitalization.

In this case, trying to target a user won't always get a $msgtag, but instead I'd make an API call for it.

Code:
 alias displayName {
  var %j = followUser_ $+ $ticks
  JSONOpen -ud %j https://api.twitch.tv/kraken/channels/ $+ $1 $+ ?= $+ $rand(1,1000000)
  var %displayName = $json(%j,display_name)
  return %displayName
}


When you want to use it, just do $displayName($nick) or anything that needs to go in that spot in place of $nick.