You can validate the field with whatever you want. It's going to be your data that you have to deal with later. Don't want users to use comments in emails? Don'

You can validate the field with whatever you want. It's going to be your data that you have to deal with later. Don't want users to use comments in emails? Don't validate them. There is not reason whatsoever to validate to a standard just because it's a standard. Validate to what you will support.