Do you filter your fiction?

I was recently told by an editor that I use too many 'filters' in my novel manuscript and I should remove them. What is a filter, and why are they bad? – A question asked by several of my editing clients.

First, I'll point out (as I frequently do) that I don't believe in hard and fast rules that say 'never do this' or 'always do that.' But there are writ…