Many engines have the potential to go past TBO if they are babied: no flights under an hour, cruised at 60%, flown frequently, reduced power take-offs, meticulous maintenance, etc.

Read that whole thread you quoted again. The guys getting well over TBO safely are doing oil analysis. Somehow I doubt this owner is taking this extra step. Also, the pipeline 172 with 6000 hours on the engine is probably flown every day, several hours at a time, with very few power changes, by a guy who knows abusing the engine will hurt the bottom line. Sound familiar?

The average 150 engine has a pretty tough life. As someone else said, full power to idle to full power.... repeatedly abused. They are tough, but no engine can take that kind of abuse for very long.

Passing annual... who did the inspection? his guy who knows he wants to dump it, or Your guy who is trying to protect you? For example, a part may show 0.005" of wear and pass, but if the limit is 0.005 it WILL need replacement at the next inspection. If I owned and wanted to keep the plane, I would replace that part for my own peace of mind. A guy selling the plane would probably say, "If it passes, it passes. Don't replace it." An engine that is over TBO probably has many parts very close to limits.... which is why there is a TBO.

This airplane has NOTHING going for it: bad interior, bad paint, bad engine, and crap avionics.

But...

You could buy it, fly it a couple hundred hours hoping nothing breaks along the way, and sell it for $10,500..... assuming you can find a sucker who thinks he is getting a deal.