This seems more complicated than it needs to be.

A shorter version below so you can understand my comment above.

alias searchnick { 
  var %t 1 | while (%t <= $nick($chan,0)) { 
    if ($1 isin $nick($chan,%t)) { var %snick $addtok(%snick,$nick($chan,%t),32) }
    inc %t
  }
  $iif($isid,return,echo -ag) %snick
}

Or if you wish to keep it one name per line.

alias searchnick { 
  var %t 1 | while (%t <= $nick($chan,0)) { 
    if ($1 isin $nick($chan,%t)) { echo -ag -> $v2 }
    inc %t
  }
}