Could you please set the 'Underscore' (_) as an alternate key on the first level keyboard?
underscore
As a workaround, you could include underscore in the list of punctuation to show in the suggestion bar (Settings -> Text Prediction -> Custom Punctuation)
Thanks for the hint, but unfortunately this doesn't work within a word (like in "pass_word")...
I'm now a bit reluctant to add alternative characters on the default English layout, as each time I tried to do I was flamed with complaints immediately (as it has some side effects)...
wouldn't it be cool if we just add the underscore above the comma key as the alternate? for those who don't put the mic key there.