Chekhov's petty details lend themselves to comedy as well: the humor in Voynitsky's entrance is clear. Thus we cannot close this discussion without noting how the tragedy of these first scenes is interlaced with comic elements (indeed, Chekhov, famous for his ability to meld both genres, lamented that his plays were interpreted so tragically). There are a number of obvious examples of humor here: the "unprepossessing" Telegin or "Waffles" is held up for ridicule. Voynitsky's caricatures of his mother and the professor are hilarious, posing him as a sort of bitterly comic misanthrope, the character who explicitly and insightfully points out the miserable nature of those around him.
There also appears some subtle moments of humor. For example, when Marina offers Astrov something to eat after his first speech, she perhaps both ironizes his endless oratory (one wonder if she is really listening) and reveals herself as oblivious to these ruminations in her blind religious faith. Such an ironic interpretation of dialogue would find new voices in Chekhov's text alongside its manifestly tragic content: in this case, voices that criticize an indulgence in introspection as well as a simple-minded religiosity. In blending the tragic and comic, Uncle Vanya allows for endless flights of fancy along these lines.
[Additional note: the verse Voynitsky quotes in his tirade against the professor is from the I.I. Dmitriev's 1794 satire, Somebody Else's Doctrine. As the verse suggests, the satire's main character lacks talent in writing poetry.]