I didn't know that references to other files are highlighted. Can you give an example? If I do in a.md:

b.md

and create b.md, nothing is rendered specially.

Similar proposal for URLs: #97

Yes, this is similar to treating URLs. @cirosantilli , did you mean ticket #10?

Using the default ikiwiki index file, it has the line below and [[SandBox]] is highlighted.

All wikis are supposed to have a [[SandBox]], so this one does too.

It could be a different plugin though. No idea if a differrent plugin does this. No I realise that this is not official Markdown syntax. But it could be a bug that this is highlighted at all.

Ah understood. For me currently it just highlights as stuff inside single square brackets (wrongly supposing it is a regular link [a](b) because there are no parenthesis afterwards): the double square brackets are not treated specially:

[                       link marker
    [SandBox     inside link
]                       link marker
]                       regular text outside

Of course, such double square brackets Wiki style links could be supported here as an extension as others have been.