Here's a question/request which ought to be easily feasible:

can we make sure that the alignment between using a module on a rack and what appears in the info section of the module in regards to usage is 1:1 ? I mean, I'd like to be able to see exactly on how many racks a module is being used on, no exceptions.

I guess you mean the section "Related Rack" ?

Right now I have a module hidden, which I uploaded and had to remove, which is in no racks (supposedly) but when I try to delete it, it doesn't allow me as "it's being used in some racks". There's probably someone who still has it on a rack but I can't know who or how many there are, since the information is non-existent.

Same goes for when I upload a module the first time, I put it on my rack and there's no info about it being used anywhere. It's a bit weird. Is it possible that it's a bug?

ModularGrid uses a system where a html page is constructed from several "partials". Single partials can be cached for performance reason. That is the case with the Related Rack partial. It is cached on the server for 2 hours, because I did not thought that it is timing critical info and if in doubt I always prefer speed over precision.
I now have updated the code that Unicorn users get real time data for Related Racks. Maybe that solves your issue?

Beep, Bopp, Bleep: info@modulargrid.net