Jerboa vs. the website do different things since they render Markdown differently. Markdown itself is so spartan that it doesn’t have many things users want or need, so a bunch of incompatible forks get made & everyone just pretends it is all the same when in reality, it often lies on a single tool’s implementation.
Take AsciiDoc with its verse directive or reStructuredText with its line-block directive. Both get you poetry-style newlines on demand & are a part of the spec instead of left to the implementer.
I find this pretty bad since everything seems to be compatible until it is too late & it is already adopted. I would like to see more uptake of the alternatives.