The problem with properly partial answers is that people don't always follow up.
I'd rather comment for additional information and testing, then sit down and polish up the answer. I might suggest something speculative as a troubleshooting step - but I don't know if it works.
If it's something I've done and believe it works, it's an answer. This probably only really works well on answers about processes though.
Sometimes an answer is partial cause it misses information. In these cases commenting or editing in (Someone once did an absolutely fantastic, very drastic edit I appreciated on an answer) additional information fleshes out a partial answer. That said, it still needs to make sense on its own.
On somewhere like Literature or IPS, I have no idea what a partial answer could look like. Even then, an answer needs to be enough that someone popping in has at least an idea on how to solve it.
So - if it helps and makes sense on its own, it probably belongs as "an answer" (quality is another issue). If its massively speculative, and seems like it's clarification, or just doesn't make sense, or just points somewhere else it isn't.
(for context - this is a post on meta.su on the same topic)