IMO — I don’t think we’re in a position to require that people who want to share macros with the community must do so in a way that we prefer.
There are many advantages to posting them on GitHub if that’s what he prefers, it’s easy enough for us to find them.
Now, if someone is asking for help with a macro, then I can see asking them to upload it directly to the site. It’s much easier to diagnose something when you’re dealing with the actual macro vs an image, etc.
It is not required, but it is generally the best way for other users to see and download the macro. I for one am not going to go thru 2 or 3 clicks, different web pages, and then try do determine how to download the macro.
Also, I, and many others, will NOT download a Macro that I can't first see the image of it.
If the user who wants to share his/her macro wants other users to use it, then it is better to upload it here.
It’s perfectly within your rights to have some stringent requirements if you want, but they are personal preferences nevertheless.
Still seems fairly unfriendly to respond to someone who offers their work to say “if you don’t offer it the way I want it, I’ll refuse to look at it.”
Doesn’t mean you can’t do it, of course. But if you consider how it would appear the the OP, you might realize it’s just as likely to turn people off this community than encourage them to do as you want.
Which also means that even people who don’t share your restrictions will see fewer macros from the wider community.
I see this attitude on sites like Stack Exchange where someone comes looking for help and gets shut down because they didn’t follow the protocols of those who most use the site.
Some would say it’s an opportunity for learning. Just as often (or more), I suspect it drives people away with a bad taste in their mouth.
Maybe the same request worded in a bit more as an invitation rather than an expectation or requirement would be a start.