OpenStreetMap

Just in case you're not aware, this is being discussed at https://www.reddit.com/r/openstreetmap/comments/450cus/can_somebody_please_fix_the_missing_great_lakes/ .

If you decide revert it, you should explain in the wiki about the lakes tagging as natural=coastline, because now the wiki "suggest" tagging inner waters as natural=water and not reintroduce this tag.
Note that tag natural=coastline was removed from Lake Ontario a long time ago.

No, I'm not planning to revert it; just wanted to point out where it was being discussed. See also the thread on the dev list that starts at https://lists.openstreetmap.org/pipermail/dev/2016-February/029068.html , and https://github.com/gravitystorm/openstreetmap-carto/issues/1604 , and a discussion of the technical issues (such as using way_area for rendering) on https://github.com/gravitystorm/openstreetmap-carto/issues/754 .

Sometimes there's no "best" way to map something, only a "least worst" one that takes into acount all sorts of potential problems.

Thanks for the info. The problem is there are various complex lakes for an multipolygon relation. Great Slave Lake can be a sample.
Regards.