Question: Why did you decide to use three !!! in a comment to separate slides instead of "---"

I looked through some other libraries that try to achieve similar results and found a lot of them use --- (three dashes) to separate the slides. I would argue that --- is a nicer syntax when looking at raw markdown than [comment]: # (!!!) which makes me wonder why you chose the latter.

If you consider --- a valuable alternative I would be happy to provide a merge request to add that functionality.