Well, I dunno how to write correct issue on your issue tracker so u can delete this post after making issue.
When I am at Shift+Alt+Insert mode I have a strange behavior when I'm editing my code.
First GIF when I try to TAB and Shift+TAB block of code:
Second GIF when I press delete button in this mode. It's VERY strange:
Third GIF about first gif, but with selection block of text:
Btw It will be good if u make this style of selection not as mode, but as hotkey-style.