Re stealing the abandoned caches – I did say that I didn’t agree with the Groundspeak view, but you can understand why they say it. It is up to each individual what action they want to take.
I have never removed a proper letterbox from the moor, that is, one with a stamp. What I have removed are saturated ice cream boxes that have clearly been abandoned. In my view these are only litter and should be removed. The National Park Rangers also take this view and will remove them.
However, this brings me back to something I have said many times before – the only thing that distinguishes our geocaches from litter is when they have been properly labelled as such, clearly indicating that they are recognised game pieces. Without a label they also are just litter.