Unfortunately that's pretty much the BBC's own definition of impartiality — as was articulated by its head of news a few years ago — and it's deeply flawed.
It means that issues or actors are given favourable coverage in proportion to their ability to muster or manufacture complaints. In important cases (e.g. around Israel/Palestine), this is not strongly related to the merits of the arguments.
This is not the only definition, but it does help. If they get complaints that they are giving the Conservatives too much and too little airtime then it's a good indication that they're dealing with them reasonably.
> It means that issues or actors are given favourable coverage in proportion to their ability to muster or manufacture complaints.
Only if they use this to alter their output. It's more of a contrast to the other situation where you get lots of complaints on one side and none on the other, which suggests (but doesn't mean) you're treating things badly.
If they responded to just the complaints (rather than trying to think about how likely people are to complain/praise each side) then they'd never allow a gay kiss on screen (the responses are phenomenal when something like that happens).
