I came here from a declined feature request to simulate the behavior of 'u'. They're not quite the same thing. 'u' takes the side bar away and replaces it with a drop-down type thing. 'f' takes away all the elements that aren't the article. (It's probably simplest to look at how greader does this.) If it's too similar to bother I can understand, given the work ahead of you, but I vastly prefer the 'u' behavior to the 'f' one, personally. If this request does cover both, then by all means keep the other a duplicate and I'll put my votes here.
I came here from a declined feature request to simulate the behavior of 'u'. They're not quite the same thing. 'u' takes the side bar away and replaces it with a drop-down type thing. 'f' takes away all the elements that aren't the article. (It's probably simplest to look at how greader does this.) If it's too similar to bother I can understand, given the work ahead of you, but I vastly prefer the 'u' behavior to the 'f' one, personally. If this request does cover both, then by all means keep the other a duplicate and I'll put my votes here.