Navigating back with Alt+Left inserts diamond character

What I did:

• Go to definition by pressing F2 (the definition was actually a define in the corresponding header file)
• Looked around there
• Go back by pressing Alt+Left
• Editor switches back to the CPP file, but a diamond character is inserted

I'm actually not able to reproduce it (maybe I pressed a third button or it is a specific press-release-button sequence). But it happened a couple of times with a 3.0-branch creator, and I never saw this in earlier version (including 2.8.1)