The edit box, where the target is placed, only holds a single nick.
When you click the OK (to kick/ban someone) or Cancel, the dialog closes, so the next time the dialog opens, the init event runs again. The init event runs every time the dialog is opened.

I just realized that there's an un-needed brace in the line I gave you last time right at the very end.

I have tested the following, which is a slightly modified version of yours, and it works. The modifications I made (with the exception of that line for the init event) refer to the radio buttons, but aren't required and simply make the code a little easier to read (in my opinion)

Code:
 alias kickban {
  if ($dialog(kickban) == $null) { dialog -mo kickban kickban }
}
dialog kickban {
  title "Kick/Ban"
  size -1 -1 172 146
  option dbu
  box "Victim", 1, 8 7 157 33
  text "", 2, 15 22 142 9
  radio "Kick victim", 3, 10 51 35 9, group
  radio "Kick and Ban victim", 4, 10 66 55 9
  box "Ban Mask type", 5, 70 45 95 30
  combo 6, 76 58 84 12, drop
  box "Kick Message", 7, 8 82 157 33
  edit "", 8, 15 96 142 11, autohs
  button "Cancel", 9, 132 127 32 12, cancel
  button "OK", 10, 93 127 32 12, ok
}
on *:dialog:kickban:init:0:{
  did $iif(!$snick($active,0),-b,-e) $dname 10
  did -a $dname 6 [0] *!user@host.domain
  did -a $dname 6 [1] *!*user@host.domain
  did -a $dname 6 [2] *!*@host.domain
  did -a $dname 6 [3] *!*user@*.domain
  did -a $dname 6 [4] *!*@*.domain
  did -a $dname 6 [5] nick!user@host.domain
  did -a $dname 6 [6] nick!*user@host.domain
  did -a $dname 6 [7] nick!*@host.domain
  did -a $dname 6 [8] nick!*user@*.domain
  did -a $dname 6 [9] nick!*@*.domain
  if (%bancombo.type == $null) { %bancombo.type = 3 | %bancombo.sel = $gettok($did(1,%bancombo.type),2,32) }
  did -c $dname 6 %bancombo.type 
  ;----
  did -a $dname 2 $snick($active)
  if (%kick-penality == on) { did -c $dname 3 }
  if (%kickban-penality == on) { did -c $dname 4 }
  svictim
}
alias svictim { .timersvictim 0 1 did -ra kickban 2 $($snick($active),0) }
on *:dialog:kickban:sclick:*:{
  if ($did = 9) { .timersvictim off }
  if ($did = 10) {
    %bancombo.type = $did(6).sel 
    %bancombo.sel = $gettok($did(6,%bancombo.type),2,32) 
    %bancombo.type2 = %bancombo.type - 1
    %kick-penality = $iif($did(3).state,on,off)
    ;---
    if (%kick-penality == on) { .kick $active $snick($active) $did(8).text }
    if (%kickban-penality == on) { .ban -k $active $snick($active) %bancombo.type2 $did(8).text }
    .timersvictim off
  }
}