I'm one of those weirdos that does use a swivel to attach hooklinks when float fishing. However, they are
tiny swivels of size 16 and 18 on the new scale (probably around 20/22/24 on the old scale). These are about the weight of the 8 and 10 dust shot which I invariably used as a final dropper. If I want a bigger gap from the last dropper (swivel) to the hook, I just tie a longer hooklink.
Initially, I only used the swivel when float fishing for grayling. It was mainly to negate some of the twist that grayling inevitably impart. I also wanted to exclude the need for any shot at all on the hook link. However, the decision to try them was made easier by the fact that grayling float set ups don't really need to be fancy on the rivers I fish. Buggering about with the distance of the final dropper is rarely necessary. I don't find that two foot hooklinks are required.
As I got to grips with using them for this application, and doubted that they were having any negative impact, I started to include them in most of my float fishing. The only downside is the inability to rapidly change the distance to the hook of the last dropper. However, as I invariably found that 8/10 shot, and smaller, invariably ping off the line, sooner rather than later, I wasn't losing out on much.
I've probably been using some sort of micro swivel in most of my float fishing for the two or three years now. I've no plans to go back to loop to loop connections any time soon. My hooklinks have also got shorter over time. Five or six (measured) inches is my usual, though I will make them longer if necessary.