I say that because the new mall indicates its address as Via Zinirco, 1

Hi, I think the current name is actually Via Zinirco, while Enrico Mattei is the older one.

Yes, shelter is still physically there but the sign is no longer present, also a FCE employee said that nobody stops there anymore.

I agree with your choice, I was wrong.

From the wikipedia page:
"Tavola, in alcune parti, il nuovo tracciato, a doppio binario ed a scartamento ordinario, utilizzerà lo stesso sedime di quello storico a scartamento ridotto[31]; il che significa che le due linee, per quella parte di tracciato, non potrebbero coesistere."

This old line is expected to never be used again, it is marked as "disused" and not "abandoned" simply because the rail is still present.

after searching for (somewhat) similar cases in osm, I found relation/10385844
it is too a disused railway now used as foot/bike path, on a larger scale than the one in Catania,
given that that one is simply shown as a railway, with no path, I think this segment could actually be removed

I had also thought about it, but regarding legislation is actually less clear than it seems

of course

People use this part of the old track as a shortcut

Hi Giovanni, the way that is I just traced is a path used by hundreds of people everyday. It runs alongside the railway (but realistically, also on the railway itself, since there are no more trains passing from there)