Why backticks? This isn't code. Maybe you can wrap these with 2-stars as in `**foo**` to have them in bold instead.

Also, `Macro` → `Macros`.

Also, in English there is no space before a colon.

I would phrase it like this:
`> ***Note:*** *Macros* are explained in the [Syntax extensions (3.4)](#syntax-extensions) section.`