The key is that anything above 3 gentlemen in a school does not add anything to the research speed. So, if you have extra gentlemen you might as well try to use them to steal techs. The chance of success is small, but rewarding if you succeed (at some point).
As I mentioned earlier, you can be researching one tech while trying to steal others. Especially, in the early game, if you start with a high-star gentleman, you can significantly boost your "research breadth" by stealing. A 4-5 star gentleman will have around 40-45% chance to steal level one techs. Of course, you will need repeated attempts to succeed.
I have not seen gentlemen gaining stars, but they do get extra character traits that boost research in a certain specialization. So, if a gentleman succeeds in stealing military tech, he is likely to get a boos to his military research (and stealing). Before 1.3, it was possible to just "visit" a foreign university and at times, gentlemen would pick up character traits just from sitting in foreign universities. Post 1.3, there are only two options though: steal or duel.
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