AdiIRC

Not atm, but this quick dirty script can do it:

on ^*:TEXT:*:#channel:{
  if ($nick == badnick)
    halt
  }
}

Press ALT + R (or go to Menubar -> Tools -> Edit Scripts) to open the script editor, then paste this script, change #channel with the channel name, and badnick with the nick you want to ignore.

If you want network and channel specific, you can use this instead:

on ^*:TEXT:*:#channel:{
  if ($network == network && $nick == badnick)
    halt
  }
}

You can type //echo $network in the channel window Editbox to get the network name.

Thank Per!

I used:

on ^*:TEXT:*:#channel:{
if ($network network && $nick badnick)
halt
}
}

And it works perfectly.

Hmm... It appears the script doesn't really work for me, all nick gets gets ignored with that script.
The only thing I see when using the script is join and quit messages.

I made a type, it was missing a *{* character, sorry about that.

on ^*:TEXT:*:#channel:{
  if ($network == network && $nick == badnick) {
    halt
  }
}

If I put it like this, in one line, it works.

on ^*:text:*:#channel:{ if ($network == network  && $nick == badnick) halt }