Posting this question somewhere more on-topic than where I'd been discussing this issue previously.
I'm an ESTJ with a lot of NFJ friends and family. I appreciate their interpersonal savvy, kindness, and creativity. They appreciate my steadiness and directness. I've heard from other NFJs that STJs appeal to them because they can take overwhelmingly detailed situations and reduce them to a sentence or two -- which calms the NFJs down immensely and helps them take action.
I acknowledge, here, that NFJs require time to Ni-Ti-dump, which I've talked with other NFJs on the forum about before. They need someone to talk at, so they can lay out all their thoughts and put everything in order. For an STJ, this seems like a prime opportunity to reduce that dumping to a brief summary and piece of advice -- which, as stated above, is one of their great strengths. They recognize this about themselves, and if they know NFJs well, they know that NFJs don't just appreciate that skill, but sometimes NEED it as well.
I haven't put a lot of thought into your specific questions, so my reply is going to be more general information that might prove to be useful.
So, I'm having a difficult time recognizing when NFJs are using me as a sounding board without wanting my input, versus wanting someone to calm them down with Si-Te quick and reliable conclusions. In both cases, they vent at me and are stressed. In neither case will they ask me for my input. Sometimes they thank me, sometimes they are dissatisfied because they wanted me to give external validation (for their Fe), and/or just listen without presenting anything for them.
I think you're SOL with telling the two apart because I think we can't even tell them apart. I've had times where I'm venting just to vent and someone throws a piece of advice out and it hits just right and gets me to stop venting and move towards putting a solution into action. Yes, validation feels good and calms me down, but it generally doesn't end up moving me towards a solution. I'm coming to believe that most of my venting has been unproductive in the long run. I now think I vent because I see a problem and I see some sort of solution (this is how it
should be) and I'm looking for ways to enact that particular solution, to the exclusion of other solutions, but I'm missing information or tools that will get me to that preplanned solution. Or I could have the tools and information, but I don't like any of the possible solutions, so I'm avoiding doing anything. Or, my ideal solution is just so unrealistic that I will never be able to act on it. So, reframing what you said, venting can be a way to look for those tools and information and/or it can be a way to calm my own anxiety about the situation without actually having to deal with the situation.
Now, most likely any ideal INFJ solution will involve not causing conflict or discomfort, so any suggestions that might involve conflict or discomfort will automatically cause me discomfort and be dismissed as undoable. I can think of two possible ways around this, but there's no guarantee that they'll work. One is choreographing the dance--you know what I'm talking about. This seems to me to be a similar area in me that I see in my big sis--a place where I'm reluctant to move from a safe place and risk change. I think I've seen suggestions that fit this idea in your blog--so you would validate, but also cause some discomfort in order to get the dance to shift a little at a time until new steps have been accepted into, and become part of, the dance. Two is modeling the action you think will work rather than just explaining it. Again, this seems to me to be a similar area in me that I see in my big sis--a place where I need to physically have something shown to me, see that it works, and then practice several times until I get it and feel comfortable with it. So, you could point out to the INFJ that the next time the situation comes up and it's appropriate for you to do so, that you will do what you've suggested so s/he can see the suggestion in action and see what results from it. If you want, you could offer to role play with the INFJ so that s/he can practice. Both of these will involve work on your part, so it's also perfectly fine to decide that you don't want to put that much effort into it and choose to tell the INFJ directly that you like him/her, but you no longer want to listen to the venting. Be prepared for some INFJs to take this personally and pull away from you.
Not to mention, it's also impossible for me to distinguish that Ni-Ti-dump process, which is normal and natural, with a Ni-Ti loop, which is unhealthy. This is because if I were ever to dump information on someone similarly, it would NOT be healthy or normal, and I would need someone to snap me out of it -- because I don't use Ni or Ti and therefore don't process similarly.
Thoughts?
The off-the-top-of-my-head answer is that with the Ni-Ti loop you wouldn't see any forward movement towards solving the problem. In fact, you might see things getting worse--as in the complaints getting more catastrophic over time.
ETA: I was re-reading what I wrote and thinking that gosh, I'm a lot of work to deal with.
ETA2: @bolded--Yeah, I can be bad about asking for input. Sometimes I think I'm asking for input, but I'm doing it indirectly and it's not understood as asking for input.