Clarity around Display Names

[Graeme S.]

I set display names to only accept "alphanumeric characters (letters A-Z, numbers 0-9), hyphens (-), and underscores (_)."

But there doesn't seem to be a way for me to tell users of these restrictions, so they have to just guess. The error message is very generic: "That value is not allowed."

Any chance we can get a custom error message for this so we can give users more guidance?

[Joel R]

You should be able to edit the language strings under Translation tools.  

[Graeme S.]

Just now, Joel R said:

You should be able to edit the language strings under Translation tools.  

It's not immediately clear if this string is only used for display name. The way it's written, my guess is that it's used elsewhere.