Windows 10 Pro x64 - pretty much stock everything, i9-7900x, 32GB, EVGA RTX3080, NVME drives, stock Windows 10 installation and DISM/SFC say no issues found. Multiple versions of drivers used. Problem has persisted for years. Starcraft, WoW, DII Remaster do NOT report this problem: it is unique to D3.
While it has never stopped the game from working, some new weirdness points to the issue having more nefarious effects. E.g., I see keyboard and mouse bounce issues when playing Diablo III, and nowhere else. I even bought a new mouse and keyboard, but the new devices have exactly the same issues; and trying other older devices that work in other computers are showing the same bounce issue. Playing Wizard, 1 key assigned to Teleport-Wormhole, the teleport often double fires, using both ports in one click – hop-hop instead of HOP.
Logitech and Microsoft are affected by this issue, as are generic keyboards. I can type all day in Word without any double-taps, but five seconds into D3 and the bounce is happening.