[bug or feature] "crossdressing" modules

It seems as though you can put armor, shield etc. on weapon slot… sorry for the title but the word crossdressing comes to mind…

do everyone have that? or is that not supposed to happen…

Yes, it is intended to work like this.

From the manual:
Standard modules have square icons and slots whilst hardpoint modules are shown by a hexagonal icon and slot. The trick is remembering you can put a standard module in a hardpoint slot (a tragic waste of destructive potential), but not vice versa.