As others have mentioned:

* $$2^n$$ for latex, renders fine on all browsers

* ![]() for images

* []() for links, including cross-links

    ** The link syntax is [<text to link>](<link path>), so for example [this is a link](http://google.com)

    ** Markdown ## Headers have an anchor with their name (e.g. `#Headers`), so you can cross-reference any other 
    section of any other note in the git repo by just using [see this section](./path/to/other/note.md#that-section)

I have a simple CI service on my git repo that checks for broken links, so that if I move a file I get a CI error if there are broken links to it.

cross-links is supported by some editing tools. (For example I use MacDown it does that.) It is not part of the MD spec. I do not use org-mode, but I know it well enough to admit it is unbeatable.

$$ for latex

![]() for images

[]() for links