So I just decided to do a bit more sleuthing, and it turns out this is a known issue that may not presently have a fix:
http://answers.microsoft.com/en-us/insider/forum/insider_win...
Bummer.
http://answers.microsoft.com/en-us/insider/forum/insider_win...
Bummer.
I'm mostly neutral on this because I don't really use window snapping, and I very rarely use Windows as it is (KDE's multi-monitor handling is OK, probably not the best, but it works well enough for me). That said, I do feel Windows 10 is a moderate improvement over 7, but I still wind up using DisplayFusion since I like its taskbar features better.
The 6-pixel "snag" point between monitors (top and bottom) is infuriating to me, and I've yet to find a registry fix that actually works to get rid of that nonsense, neither can I find any obvious settings for it. Any suggestions?