You're welcome! No, you don't have to download anything. Just open a new account in FiiO's bugzilla page. After that you will be able to comment and vote for existing bugs (as well as to submit new bug reports). There are two limitations in voting though: Each user has 25 votes in total and can at most give 3 votes to one single bug.
There are a lot of advantages in using a bugtracking system like bugzilla over a simple webforum like head-fi which I tried to summarize here. I think the most important benefit of the voting feature is that one can see instantly which are the most important issues (i.e. buzzkillers) which is helpful for users as well as the company and their developers. Of course this requires the participation of as many users as possible, therefore I hope you'll join the 294 other users which already registered an account