None of the characters that are expanded fall under the range of characters that wouldn't already produce a salt character of ".", and they can all be represented as characters with the high bit set with no change to the resulting crypt, so that's not a point that you really need to worry about, and really, doing those checks is just a waste of processor power.

Some equivalents:

# = ｣
! = ｡
< = ｼ
> = ｾ
& = ｦ
" = ｢
' = ｧ
, = ｬ

If your tripcode searcher checks all characters from 0x1 to 0x7f, and checks all applicable combinations for salt values, you're getting the complete range of possibilities, and with a bit of finagling, any tripcode it generates can be converted into a format acceptable for use on a board, without needing to do any complex and expensive html conversions.