It seems that usually it is talked about snapshots as read-only. (In a scenario where one creates a snapshot, then does some experiments with the main volume, and then restores the old state by "merging" the snapshot into the main volume.)
Is an alternative scenario possible in LVM? I.e., where one doesn't even want the temporary experiments to be visible in the main volume, so one creates a "temporary" snapshot, makes it writable, does the experiments there, in that "branch", and then discards the snapshot (or perhaps merges it if one is satisfied with the results)?
And if writable snapshots are possible in LVM, then what happens when merging a modified snapshot into the main volume which also has had some different modifications?
(BTW, btrfs snapshots seem to be writable by default, so this scenario seems to be well possible in btrfs.)