I know that shortcut for CTRL + K + D is only for Visual Force pages but it helps a lot also with Lightning Component development where we also have a lot of HTML tags.
The problem is with some lightning component for example:
<lightning:icon iconName="utility:down" />
After using CTRL + K + D will change into this:
<lightning:icon iconname="utility:down" />
The only change is all upper case letters are turned into lower case letters and the icons stop working.
This is only one example that I found but I believe this will also affect other component where case-sensitive is required.