I have a hyphen in my name. My name is spelt “Anna-Kay” in my passport and all legal documents.
Its not that unusual a character to have in a name, but some forms disallow any characters which aren’t A to Z. For example:
The problem with this is that it causes me to error on forms which haven’t been set up correctly, and is a user experience problem resulting in me having to spell my name: “Anna Kay” or “AnnaKay”. Neither of the above are my names, and it becomes extremely frustrating to submit a form for it to be returned to me because the site doesn’t handle special characters in names correctly.