Certain Characters Prevent Contact Category Links from Working

I had originally posted this as an issue with the "Contact List & Forms" module (Certain Characters Prevent Contact Category Links from Working), but have been told it is actually an issue with the core contact module, which is why I am reposting it here:

When adding in categories to the contact list, most characters can be used without a problem. However, I have noticed that three characters in particular do cause a problem if they are present in a category name, and that category link is clicked on:

• The plus sign (+) causes the page to redirect to itself (only once - it does not get stuck in an infinite loop).
• The slash (/) does the same as the plus sign, but is not encoded in the URL containing it (it's shown as "/" instead of "%2F").
• The backslash (\) generates a 404 error. What's interesting about this is that - in this case - the error is from the server instead of from Drupal.

Out of curiosity, I added one category which was a string of every ASCII character available in the "Character Map" in Windows (broken up into 20 characters per line here - the soft hyphen isn't visible, but it's there):

!"#$%&'()*+,-./01234
56789:;<=>?@ABCDEFGH
IJKLMNOPQRSTUVWXYZ[\
]^_`abcdefghijklmnop
qrstuvwxyz{|}~€‚ƒ„…†
‡ˆ‰Š‹ŒŽ‘’“”•–—˜™š›œž
Ÿ ¡¢£¤¥¦§¨©ª«¬­®¯°±²
³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆ
ÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚ
ÛÜÝÞßàáâãäåæçèéêëìíî
ïðñòóôõö÷øùúûüýþÿ

When the three characters mentioned above were removed, the string worked just fine. Could there be an issue with how they are encoded that is causing issues with contact category links containing those characters?

Though this issue was not found without the use of the "Contact List & Forms" module, would other modules that require contact.module to be enabled also be affected by this?