For places you’ve been to some time back in Arc’s history, it’s very the source was Foursquare. Newer places (within the past year) will have come from either Mapbox or Google Places.
All of them can be merged, if you’ve used multiple different ones for the same place, and want to tidy them up. Glad to hear you found the Place Merge feature!
The street addresses shown for each place are taken from Apple’s addresses lookup service, rather than from the original places source (ie not from Foursquare, Mapbox, or Google Places). This allows me to use a single consistent service for getting street addresses.
Although I’m tempted to experiment with using the street address info from the place providers, in the hope that it will be more accurate. But in many cases in the past, unfortunately it hasn’t been, or have varying qualities of formatting and detail. At least using Apple’s auto address lookup for that gives consistency in formatting.
For the icons, those again are a hodgepodge of sources. Foursquare did provide icons, but they were of low quality and didn’t match well with Arc’s design. Mapbox also provide icons for a subset of their places, which Arc does use when available, because they’re close enough to Arc’s design style. I think Google Places do provide a very limited range of place icons, but if I remember right, they were so limited as to be next to useless. So for places from Google, Arc maps the category names to Arc’s own icons, same as it did with Foursquare places.
Heh. Basically place databases, place metadata, and place icons are a messy vortex of confusion! Over the years it’s devolved into a situation where there’s no single reliable source, so the resulting hodgepodge is what we get. Arc tries to make the best of what it can, but yeah, sometimes it doesn’t come out in the most ideal way!
One thing I do have on my todos though is to at least show in the place results lists the source of each place, to make it a bit easier to disambiguate. Ideally it shouldn’t matter where it came from, but in practice it does tend to matter quite often.