This SPARQL properly deletes the intended triples (Community v5.2.0)
WITH http://www.example.com/
DELETE { http://www.example.com/d7e230bf-502d-438b-b3d8-d66326f3c7d9 ?p ?o. }
WHERE { OPTIONAL { http://www.example.com/d7e230bf-502d-438b-b3d8-d66326f3c7d9 ?p ?o. } }
The same SPARQL against a deployed cluster (v5.2.3) results in a 500 internal server error.