This has always confused me a bit and the answer might just end up being "it depends," but I was wondering if there's a way to properly evaluate this.
For example if I wanted to ask "Is this a shared PC?" I might say
このPCは共有用？ and I'm not sure if that means
共有している。I almost always think されている sounds better but as for whether
共有する is transitive or intransitive or not - I don't know. As for which sounds stranger to Japanese people I get the impression that in the case of 共有 leaving out する and its conjugations all together is better.
I know that for intransitive verbs its simply the stative form of it, for example "It's been decided" is
決まっている rather than
決められている, but the differences in nuances of those two I think has to do with how direct you want to be, and whether the agent of the action is knowable. Obviously I might be trying to apply logic to this that doesn't work but...
Another example that confuses me:
"Is this applicable to everyone?"
My intuition tells me that using される vs している means that there is some agent in the background or contextually that had an influence, whereas している just implies that it is a certain way. What's a good way to think about this?