In the current going elections, I am willing vote to a one user instead of three. Is my vote for one user will be counted? or I should compulsorily vote for 3 users?
PS: I know only one user and I know he is definitely eligible to become mod.
Votes are counted using a system of Single Transferrable Vote (STV) counted using a system called Meek's Method.
Unless I misunderstand how STV works, it is not compulsory to vote for 3 users. One vote will still count. However if you vote for one candidate and they are removed from the race, then your vote will not transfer to another candidate. By reading about the other candidates and selecting a 2nd and 3rd choice, you can still influence the result even if your preferred candidate is unsuccessful.