I'd be a bit skeptical about that autotrader review. I can believe someone having five parts
of an engine replaced (EGR springs to mind), but even that would be bad luck. Five whole engines would be more than the value of the entire car. Doesn't seem credible.
As for the 2.4 JDTm, it's a perfectly robust unit, albeit that - as a diesel - there is more to go wrong than the equivalent petrol powerplant. The cam is belt-driven, so as with all belt drives, a clean service history is very important. The nominal replacement mileage for the cam belt is 90k miles, but many on here get the cam belt changed at 72k, or 60k as a precaution.
The predominant issue, as stevepen above suggests, is the diesel particulate filter clogging with lots of short runs around town. A good blast on the motorway, or regular motorway miles normally sorts that out, but if your predominant driving style is 'around town', then I would recommend the 2.2 petrol. The EGR valve is also prone to clogging in the same manner.
One minor issue with the 2.4, is they came fitted with a plastic bleed screw at the top of the water cooling circuit, above the engine, which is prone to failure. It's a very easy job to replace this with a "proper" metal screw, and it's essential that you get this done. Do a search on here to find more information.
Other than that, its all good!
The 1.9 is the 'sister' engine to the 2.4 (effectively one cylinder lopped off the end), so much of what I've said still applies. The fuel economy isn't as good as the best of the Germans currently, but in terms of 'smiles per mile', it's far better.