So, This is my shot at a 1 time nick response thing, for when you're afk. All you have to do, is /a (reason) and the rest works itself out. The snippet will check if they're in the variable, and if not, it'll give them a notice saying you're away, why, and how long. Then it adds the nick to the var. It works for text in a channel, and for when someone private messages you.

alias a {
  set %names 
  away $1-
}
on *:text:*:#: {
  if ($me isin $1-) && ($away = $true) {
    if ($nick !isin %names) {
      notice $nick $me is away. One-time response to nickname highlight. Away Reason: $awaymsg Been gone: $duration($awaytime)
      set %names $+(%names,$cr(32),$nick)
    }
  }
}
on *:text:*:?: {
  if ($away = $true) {
    if ($nick !isin %names) {
      msg $nick $me is away. One-time response to nickname highlight. Away Reason: $awaymsg Been gone: $duration($awaytime)
      set %names $+(%names,$cr(32),$nick)
    }
  }
}