A. The problem isn't the "/" character, your regex seeks "amp" which is also in "timest[color:red]amp[/color]".

B. $nohtml (incuded below)

C. Although you didn't ask whistle, you don't need to silence /sockwrite

Code:
alias irct { sockopen irct forums.mirc.com 80 }

on *:sockopen:irct:{
  if ($sockerr) { return }
  sockwrite -n irct GET /ubbthreads.php?ubb=postlist&Board=5 HTTP/1.0
  sockwrite irct HOST: forums.mirc.com $+ $str($crlf,2)
}
on *:sockread:irct:{
  if ($sockerr) { return }
  var %x | sockread %x
  if ($regex(%x,/&amp|#Post/)) {
    if (	<a href* iswm %x) { %irct = 8,1$ +([,$nohtml(%x),]) }
    if (<span class="small">* iswm %x) { %irct = %irct 15,1was created8,1 $nohtml(%x) }
    if (<a href=*User*nofollow* iswm %x) {
      %irct = %irct 15,1and 8,1 $+ $nohtml(%x) 15,1was the last person to post.
      echo -a %irct
      unset %irct
    }
  }
}
alias -l nohtml return $remove($regsubex($1-,/(^[^<]*>|<[^>]*>|<[^>]*$)/g,),$chr(9))


Edit: fixed parenthesis mismatch shocked