What can be done about an unintentionally disruptive classmate?
It sounds like everyone who's dealt with it decided the student's behavior was a minor annoyance at most, or even that their questions were valid and worth answering. Repeating material that was covered in previous lectures, in the syllabus, or on the website is...well, part of the job, and many professors explicitly welcome questions about past material or any general course questions of that nature. It is generally assumed that students aren't tape recorders with perfect memory, and if a professor is really bothered by it they are free to answer with "that's covered in the syllabus". Off-topic questions are typically easily handled with "that's beyond the scope of this course, so questions like that would need to be asked in office hours/email/someone else." If the professor goes off on 30-minute tangents about meatballs because a student asked a question about them that has nothing to do with the course, well then you'd have a valid issue to raise with the professor.

Based on your descriptions, all the past professors found minimally disruptive ways of handling less-than-perfect questions - such as limited answering, ignoring comments that did not need a response, etc - and found a way to move past it. If there is regular behavior by another student that rises to the level of such a disruption that you feel you are materially harmed in your education by being subject to it, by all means bring it up to the appropriate faculty/administrative contact.

However, I must point out that there is a baseline reality that standard deviation in the human population is greater than 0; people are not all the same.  This means that your standard of behavior will not be followed by everyone, and others will have different standards of behavior than you do. It often pays to first ask yourself: "is this so far out of line that it I really need it to be dealt with?" If it's just an annoyance, or something that really isn't really that big of a deal, empathy and patience might be a more useful strategy than complaint. 

As to how a potential complaint would be received, that rather depends on what you are complaining about. If you complain that a fellow student asks questions about the class that are already covered in the course materials, some professors will agree (they wish students read the syllabus too), and some will think "that's a weird complaint, I wish more students asked, because it sure isn't like the ones that don't ask actually read it all". If you complain that the student is a bit odd, well, yes, they probably got that idea by now. If you complained that a student was, as an example, yelling racial slurs in the middle of class, then that would certainly be seen as a valid complaint, while another complaint about a student with tremors shaking and you find that distracting...not so much.

So in the end, I would advise you to consider the seriousness of your complaint. If you feel that what you've witnessed/experienced is materially harmful and wish to make a complaint, make sure you specifically address exactly what is the issue and what you would like done about it, such as: "a student regularly asks questions that are not pertinent to the course, and the professor allows the distractions to cut into class timer, or ignores continued talking and comments instead of telling the student to stop."