The bounce technique might have been a good test on a Mk1 Escort, but anyone who can bounce an RS Clio is obviously a lot stronger and heavier than me ! But the main point of the test is that if your dampers are shot, the car continues to oscillate. The springs will always push back.
When my rear damper dumped all it's oil I'd describe the rear end as wallowing in the bends with a little more roll and being a bit floaty over uneven bits on the motorway. Feeling bumpy would not have been a term I'd have used, but as you say it's hard to describe.
It did make the back a little looser but then so did the tyres when they they wore past a certain point (still well within legal limits). Oh, and the recent ice. In fact, I went through a spell of getting paranoid about the back end letting go and this made things worse as I started subconciously lifting off in corners and unloading the rears.
I guess what I'm trying to say in my morning waffle is that there are lots of reasons why the back end can come unstuck, but rear dampers are a common failure (mine went at 28K) and are a major contributing factor to Clios going through hedges backwards so if you're worried about them get them looked out. They are not very expensive (about £50-£60 each) and easily fitted by someone with a little mechanical ability so shouldn't cost much to have you local friendly garage fit them if you don't want to take it on yourself.