First of all, don't listen to anyone (or convince yourself after what you read) that any type is "incompatible" with you. We are all different, have different priorities, different expectations, values etc. If you find a "connection" and love you will find ways to work out the differences.
Now
Having said that...
In my own experience this is not impossible but it's hard :sad: . I think that a lot of people that use mbti typing to judge their relationships tend to do a posteriori. Rather than saying, it will never work out, they say..aha..this is why it didn't work out.
Again based ONLY on personal experience:
It will be a very cosy, safe relationship, where you would do lot's of familiar things, cosy nights in, very structured, predictable and dependable. Both introverts, one of you will be the more extrovert and will organise social life. I have always found that we are more flexible and can make an effort if we have to (ie be nice and sociable because the occasion requires it even if we would rather be home reading a book) whereas the ISTJs are more stubborn. If the ISTJ isnt in the mood or doesnt want to participate, it will be you making the effort for both and maybe trying double hard to make up for them not being social. A bit like INTJs you can't make them do something they don't want to, whereas we read the mood in the room, we understand what's expected and we are more likely to deliver.
The ISTJ will look after you and deal with those little everyday things that really irritates us in a very efficient way. It's up to the individuals to let it develop in a "healthy symbiosis" or a very unhealthy "mothering/fathering" relationship. The ISTJ can thrive on this role or resent they always have to do everything. The INPF could be in heaven or be patronised until they have no confidence left. Depends.
Idealism vs realism. Under stress INFP want to feel everything will be ok, somehow. They need hope. The ISTJ is more likely to do a sober analysis of the situ, predict the worst case scenario and expect the worst. In the long term this is crushing for INPFs because we pick up a lot of negativity.
If you want profound, big picture, emotional conversations in which you open yourself up to another individual and you find this amazing connection because they "get" you..find yourserlf friends or family to do this with. With the ISTJ is not going to happen. Simple, don't sweat it or you'll feel lonely. You'll find the only conversations that will work will be about practical details, immediate issues, tangible things around you...sensing territory and totally alien to us! haha.
I also think that for some reason INPFs and ISTJs can share the same sense of humour. They can be hysterically funny, in a dry, one liner, to the core in one punch kind of way.
Also little conflict, more silences, sulks and brushing things under carpet and pretending everything's fine. Both types hate arguments.
