Shapeless- I attampted to research the contention that Tchaikovsky committed suicide, but was faced with conflicting reports.
Interestingly, Grove's Dictionary, the source that the passage above refers to, has flip-flopped on the issue itself. As the article mentions, the 1954 edition of the dictionary acknowledges the lack of definitive proof; then David Brown's expanded entry for the 1980 edition claimed that the suicide could not be doubted; now the 2001 edition (in which the Chaikovksy entry is written by Roland John Wiley) has gone back to the original position: "The polemics over his death have reached an impasse, one side supporting a biographer not invariably committed to the truth, the other advocating something preposterous by the mores of the day. Neither version withstands scrutiny, making all conclusions provisional... We do not know how Tchaikovsky died. We may never find out..."
For the most part it seems like a matter of minimal importance, but it's been a tremendously important debate within musical scholarship and has had a direct impact on the way scholars evaluate his music (though it's had little effect on general listeners, for whom Chaikovsky's canonical status is pretty near unassailable). Those who dislike Chaikovsky have found it useful to use the suicide theory as an indication that his symphonies are laden with emotional baggage at the expense of substantive technical proficiency; some antagonistic scholars even used to claim that his suicide, coupled with the broader issue of his sexuality, meant that his music was "tainted" and pathologically dangerous to listen to. On the other hand, those who champion Chaikovsky use the suicide story as a way of turning the symphonies into poignant autobiographical stories that enhance the appeal of the music. (This is basically the same view as the anti-Chaikovsky stance, except that the emotional content is now considered a good thing.) This is why the suicide has remained inconclusive... it's been very difficult for scholars to treat the matter as an objective historical issue rather than as ammunition for subjective opinions about the quality of Chaikovksy's music.