I just started to use mapshare, and right away it seems to me it is sharing a bunch of stuff that I didn't give it permission to share.
For example, I uploaded to explore maps a bunch of collections... one with waypoints for waterfalls, one with waypoints for trig stations, one with waypoints for weirs. I didn't give them permission to share.
So then I activated an inreach service, and I shared my mapshare via the tracking screen, and Inreach/SMSed myself a link to the sharing page. On clicking the sharing page, I was surprised to see all these collections of waypoints. The collections containing those waypoints did NOT appear in the "Collections" list, BUT the icons of those waypoints did appear!
So going back to my explore web page, I checked on the status of these collections.... and the "M" is greyed out, indicating they are not shared. I clicked on the "M" to see what happens and it brings up a dialog box listing my collections with checkboxes of which to share. And indeed, those collections are not shared. I toggled one on, saved.. went back to the share web page... The collection appeared under "Collections"... back on the explore web page I toggled it off.. and saved, and then went back to the share page... it disappeared from the list of collections, but the waypoints themselves didn't disappear.
Sure, my list of trig stations and waterfalls is not a state secret, but sharing location data without permission is a big no-no.
Another kind-of related issue, is that the toggles in "collections manager" in the Garmin 66i also don't do anything. They don't remove those collections from the device map, and they don't remove them from the device lists of waypoints and routes. Seems to do nothing at all. Probably an unrelated bug... but then again, maybe not... because it seems like multiple Garmin products have issues removing collections from maps, and the 66i collections manager toggles are similar to the "M" enabling of collections in Explore web site. ( I've got firmware 8.80 (609013) on the 66i and Explore version 3.0 (617602) Android)