Graham
Spitfire LF.IX, the most popular or even the only available version in USSR, had a service ceiling of about 12,500m. MiG-9 theoreticaly had a service ceiling of about 12,800-13,000 but IIRC Spitfire simply flew better at altitude, while MiG suffered of several problems disallowing its combat use and was not available in quantities. MiG-15 outclassed Spit, having ceiling at 15,200m and finally replaced her in air defence units. Oh, both had RR engines.
And their enemy was initially Spitfire XIX (with performance superior to LF.IX - I think Griffon had better alt. performance rather than Merlin in Mosquitoes) and then Canberra, I think both with RR engines.
My point is not that the jet engine was a bad concept (at last jets replaced pistons), just only the level of development was not so advanced. Initially, the main advantage was superior speed and climb and not necessarily altitude. With speed advantage of about 200km/h you do not need the latter that much. Of course, the only way to intercept such a beast was to climb higher and then to build up the speed in dive. A very hard task and definetelly a job for an excellent ground control. But still, was it the reason of paint removal?