Possible, but unlikely. Kasparov may be strange, but he manifests his strangeness differently than Fischer. He's a polyglot and a mathematician. He's also pretty gregarious.
He used to be something of an activist (not that that's a credential, I suppose). Maybe as an Armenian Jew in Russia, he was a little less apt to take things at face value.
When Kasparov played Nigel Short in London in 1993 it received a lot of coverage on Channel 4. During the 'intervals' the producers ran histories and bios of the two players. Here's what I remember about Kasparov. What you say above is absolutely true - he was a boy genius and never tired of learning. He was an Armenian Jew but he became Russian towards the end of the Soviet era and now has Russian citizenship. Being a polyglot, gregarious and a strategic thinker he was recruited as a senior adviser to the Soviet inner circle - a role he still maintains with Mr. Putin and his predecessor Boris Yeltsin.
Kasparov is well read and likes to broaden his knowledge with all forms of world literature and Twain would have been a natural choice since he was coincident with the other classic novelists such as Dumas, Hardy, Dickens, Tolstoy et al. For such a clear thinker it is hard to envisage how he made such a mistake when misquoting Twain. It could not be put down to fatigue or distraction. Kasparov leads a spartan life and is slave to his routine. A luxury apartment with only simple fittings, not married, no television or radio and he sleeps for only five hours a day whilst playing up to twelve hours of chess a day. He's a healthy eater (he doesn't smoke or drink) but not an exerciser. All his other waking hours are spent reading or advising.
