When editing an HTML file with script tag and selecting one or multiple lines and hitting Ctrl + K an HTML comment (<!-- -->) is inserted instead of the valid comment for the type of tag the lines are in (// when inside <script /> and /* */ when inside <style />).
Intellisense is working inside the script tag so I guess VSCode has a way to know which language is associated with each line and could therefore input the right type of comment.
VSCode 1.54.3