From #432 (comment):

i did not see the scope write:discussion, is it because GHE admin turned it off or simply GHE version thing? mine is GitHub Enterprise 2.11.18

The write:discussion scope is a newer scope that older versions of GHE don't have (or have under a different name). Most of the features of the extension don't require this scope (it's mainly for team discussions), so it won't break functionality if this scope is optional when validating scopes.

This only affects validating personal access tokens created manually by the user for GHE hosts (not github.com), as the sign in process is only available in versions of GHE that also include the write:discussion scope.