Hello Friendly_Ghost,
Thanks for commenting this changeset.
I've been mapping Faial island over the last 9 years as a leisure activity on free time. At such a scale, you can see that at some point some growing pains are going to occur and consequently, a mapping style had to be implemented in order to make the database more maintainable and scalable. This is a continuous process.
Individual areas are effective and simple to implement, but much less scalable and maintainable. Imagine that you have a forest next to a meadow. There's now a duplicate line, sharing the same geometry. Add a wall or fence between the two, now it's a triple line. Now imagine that somewhere in the future someone build a house that occupies part of the meadow next to said forest. That'd be a big challenge to unglue things and then map the house's residential area. That's a situation where multipolygons can be very powerful. You can easily map at scale. You set a forest tag scheme for a eucalyptus forest for instance, and you just need to add the corresponding loops to the multipolygon. No need to tag every tag to every area every time.
The multipolygons became bigger over time as mapping naturally progressed. What's a big multipolygon to you? These follow the complex combination of features as described in
https://wiki.openstreetmap.org/wiki/Relation:multipolygon#Members
There doesn't seem to be a limit to the number of members, but I can see that doing multipolygon geometry validation on some computers would be very slow.
I'm currently transitioning into one multipolygon per parish in Faial island. This process is happening as I map, but feel free to help! But please don't split a multipolygon with thousands of rings into thousands of multipolygons, as It'd make editing in JOSM close to impossible, as the user would have to endlessly scroll on the relations panel.
Good mapping
Thanks