I had asked this question on Stack Overflow, but I couldn’t get a proper answer. Can you help me? Here is the whole text:
In the emphasis and strong emphasis section of CommonMark Spec, it says:
- Emphasis begins with a delimiter that can open emphasis and ends with a delimiter that can close emphasis, and that uses the same character (_ or *) as the opening delimiter. The opening and closing delimiters must belong to separate delimiter runs. If one of the delimiters can both open and close emphasis, then the sum of the lengths of the delimiter runs containing the opening and closing delimiters must not be a multiple of 3.
But I have no idea what it means by “the sum of the lengths of the delimiter runs containing the opening and closing delimiters.”
- What is it, and why it must not be a multiple of 3?
- What happens if it is a multiple of 3?
Edit: I found the demonstration on the same website and there was a code
> ([source](http://spec.commonmark.org/dingus/commonmark.js)). My rough understanding is that this rule was intended for restricting three-character delimiter runs in the middle of alphanumeric characters. (e.g. "\*\*\*hello\*\*\*" will be rendered to be ***hello***, but "\*\*\*hello\*\*\*world" will not be rendered.) However, I'm not sure if my understanding is correct, and why such restriction is needed if I understood it correctly.