Can the Backchannel-Logout feature in IdentityServer 4 be used to reject a Logout-Token resulting in a bad request?

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Yes, the Backchannel-Logout feature in IdentityServer 4 can be used to reject a Logout-Token resulting in a bad request. When a Logout-Token is received, the validation of the token can be done, and if the token is invalid or if some required parameters are missing or incorrect, a bad request response can be sent back to the issuer. This ensures that only valid tokens are accepted, and helps to prevent any unauthorized or erroneous logout requests.