There are already extensions to Markdown- that's the reason for the CommonMark fiasco. They wanted to standardize so that people could know that this version of Markdown was the supported version. That was shot down by the creator in a passive-aggressive fashion. So they just created CommonMark which is a semi-standard. From what I saw in there, they're using the CommonMark short link annotation standard now.
From
https://www.srid.ca/5b963b1c.htmlSimplified linking syntax #59
Several users requested that the syntax for linking to zettels be simplified. To that extent, Neuron now supports the following style of links:
* This is a link to a zettel: <5b963b1c>.
* It will automatically expand to the Zettel title
that is linked in the web interface.
In short, to link to a zettel whose ID is ā5b963b1cā, you only need to wrap it inside angle brackets. We are not using any special syntax here; this is what is known as Autolinks in the commomark spec. Neuron simply leverages existing linking syntax to allow you to link to zettels; and the Neuron renderer can automtically fill in the zettel title, and other metadata, during rendering stage.
Emphasis mine. The github issue is
https://github.com/srid/neuron/issues/59. It references the syntax that you're referring to- they use this instead, so that's outdated.