What characters are allowed in an element name?

Summary:

What special characters are allowed when creating a new element and can that be worked around by update/correct on the element name after creation?

Content (required):

When creating an element, the process fails if there are any special characters other than a dash and underscore in the name. But after creation you can correct the element to have a different name that includes various characters and it seems to accept that.

Element Name Naming test -_()*&^%$£ (this seems to be allowed after creation)

Element Code Naming test -_ (this appears to be all you can have during element creation)