While the situation you describe does sound quite close to comfort I seem to share Di Voshs train of thought. Do nothing, you dont know who is in the other aeroplane, their credentials, abilities, local knowledge, reasons for doing so etc. You said it yourself, he has not broken the law. Personally I take intersection departures all the time as well as a bit if tailwind if it suits me. If anyone decided to shove their conservative views in my face I'd tell them to get nodded. For everyone that does everything according to OWT's I think it's good that some people think for themselves and operate with a bit of flexibility. Again the story described does sound like pushing it though.
in an Arrow and got offered an intersection departure off runway 23 to put me ahead of a Fokker and a 737 who were taxiing ahead of me, would have had 1000+ TORA, but declined
Private Op I hope.