In theory, everyone should allow every character, but special characters have caused issues for so many devices that I have used over the years that I gave up on them long before I got a Roku. Even one of the routers I had wouldn’t allow them. You can find much about this on the internet. For example, one router maker says: While Some Special Characters are allowed, it Is Not Recommended Due to compatibility issues with some smart devices such as smart cameras.
Banned but back. Because why not?