Are questions about PATA, with no other Retrocomputing-related elements, on-topic?
IDE/PATA is per se (*1) not on topic, as it's still actual technology (2018). Drives are still sold with PATA, even new Flash drives are fited with PATA. Same for mainboards with IDE/PATA. Just bought one last summer, as I still want to keep my LS240 drives running. There are PCIe adapters for IDE/PATA available, as well as USB-IDE/PATA bridges.
To be on topic a question needs to have a clear RC related target. This does include issues like (non-exhaustive list)
(in general, "old" refers here not so much to age, as outdated, no longer manufactured/sold and no longer maintained)
Problems with a certain combination of (old) adaptor/mainboard and (old) drive.
Informations of specific protocoll issues/enhancements of special no longer manufactured and maintained drives.
Hardware problems with (old) adaptors/drives in their retro environment.
Documentation Requests for such drives/adaptors/mainboards.
Drivers for (special) drives for a retro environment.
Shoping recomendations for spare parts for no longer produced/general availible hardware and/or software (I know this is controverse - but here the crowd mind is needed)
Other Issues are rather borderline and do need a case by case evaluation, like
Connecting an old drive to some odd machine. While this is in general off topic, if the machine is odd enough, curiosity/cooless of the solution may outwight this.
Connecting an old drive to an actual machine for continued usage
Connecting an old drive to an actual machine for data recovery
Looking for (non standard) drivers for modern OS to use old drives.
Ofc, especially point 2/3 is only on topic if there is no standard, common available off the shelf solutuion available.
Addendum: Thinking of it, these rules may work well not only for IDE/PATA, but any technology. Wheels are still round, so many old technology can still be found new of the shelf. So taking above guidelines may work as guidelines to see if a certain question is a case for RC, or some other Stack.
*1 - Per se, Latin for by itself