[erlang-questions] What is "Abandon carrier utilization limit" for?

[Roger Lipscombe]

What does it mean for a carrier to be abandoned?

The documentation says that if an allocator needs another carrier,
it'll re-use an abandoned one, which doesn't sound very abandoned to
me.

Can the VM move blocks from an abandoned carrier to a new carrier? I
assume not, which means that abandoned carriers can't (easily) be
returned to the OS.

Or is it that, once a carrier falls below the threshold, the VM tries
not to use it, so that it's more likely (assuming that the remaining
content eventually gets freed) that it'll get returned to the OS?

Also: what is the default setting? The documentation says "de", but
system_info is saying "0" for all of my allocators. Is "de" choosing
zero for me?

Cheers,
Roger.