PaperTiger,
All of the types you mention with square windows attained far lower altitudes than the Comet, therefore the pressure differential was a lot lower and the stress/strain cycling a lot less. They could use square windows no problem, the Comet could very obviously not.
The British aircraft industry certainly learned a lesson from it though, going from paper thin skins on the Comet to over engineered "brick !!!!!house" designs, i.e VC10, Trident, 1-11......