[kuschku]

On international keyboards, there is no right alt key, but instead at that place is [AltGr], which triggers both [Alt] and [Ctrl].

[AltGr]+[M] for example gives μ, [AltGr]+[E] gives € and [AltGr]+[Q] gives [@]. Obviously, [AltGr]+[←] doesn't work.

It's one more of those shortcuts that make it obvious that whoever made the decision only ever used a US Standard keyboard, and never even considered international users. The only decisions even worse are ever using ` (it's a 4 key combo on some international keyboards, and not at all existing on others), or ~ \ [ ] { } ( ) ; : (all of these are combinations of usually two or three keys on most international keyboards).