"Also the M+D jet is not a model engine and wasn't based on one. It was designed built and certified as an aircraft jet turbine by a certified manufacturer."

That is not true in the slightest. The engine was designed by what can best be described as an 'enthusiastic amateur'. M&D entered an arrangement to use his design and continues to buy certain critical parts off him, per their contractual agreement. The fact that some of the installed fleet are 'certified' shouldn't aid your sleep in any way. The requirements for performance, reliability and failure containment that apply to the jets power commercial aircraft don't apply.

High altitude starting

I haven't experienced the same problems others are referring to, though my starts are most often around 2,000ft AMSL. My lowest temp start has been 10deg OAT and highest 40deg OAT. I use Jet A1 and Aeroshell Turbine Oil 560 exclusively. My highest altitude start was at the factory, perhaps 6,000ft AMSL without issues.

Reliability

I know of a number of fellow owners of the same type that have had huge problems with their jets. I had escaped such troubles until the 2 year mark when I had a series failed starts during pre-XC tests (I have an inflight test-start requirement of the first flight and then once per week after that, on aerotow). The culprit was a compressor housing O-ring that had broken in several places. Snicked during installation due to a weakness in the design and failed over time. Post replacement, performance returned to is regular, exemplary level until 'the failure'.

"Anyone know the cause of the turbine failure first mentioned in this thread?"

A failure of the main bearing due insufficient lubrication. The reason for this was not determined. The tube to lubricate the bearing is remarkably thin, it doesn't take much to block it. There is no fuel filter downstream of the aircraft-engine connections in the fuel line, another design weakness

"How much damage was done to the airframe when the engine failed?"

With successful operation of the jet established, the pilot departed the chosen outlanding field. 'Hopping' from landable backup to laudable backup field, at the point of failure the pilot entered the circuit for a pre-selected field and landed safely.

Overall, I'm cautiously happy with the jet (so long as I don't experience a repeat of this failure!)

CJ