In wiktionary in chrome, when the focus is in the editbox, pressing Ctrl-U opens page source view.
In wiktionary in firefox this also sometimes happens, but the condition seems to be intermittent.

The problem doesn't occur in wikipedia in chrome. This is possibly because syntax highlighting is turned on there.

Sometimes I have to struggle to enter a UNICODE character into wiktionary because both browser open page source view.

Ideally, IMO browser shortcuts should be disabled in the editbox.
But for me, Ctrl-U is the one that causes problems.

And why is this behavior variability?