I had a thought.
It seems that a lot of times, ISFjs are (or can be) compared with INFjs, or other types I suppose, and called unforgiving and accused of holding grudges, etc.
I suppose this might seem obvious, but I think it's the Se. Se is about physical, external, concrete reality, right? So, when someone does something, there are consequences. Sometimes those consequences are nice, sometimes they aren't. To just let it go and pretend it didn't happen is in a way ignoring Se. So ISFjs have to take what happened into account, because it is reality. Otherwise I'm not sure they'd be ISFjs.
That, combined with the static mindset, means that "this is the reality of the situation; and we have to live with it". Add to that the Fi aspect, people related, and you have the makings for what is often called "holding a grudge."
However, "good Fi" I guess you could call it, can also be concerned about making the reality right. They care about the people involved and want good to come of what is.
So, while ISFjs can hold onto reality and the consequences of decisions, they are not necessarily unforgiving or unkind. In fact, I would think that they could be quite good at knowing how and being able to shift the reality to help alleviate the consequences, or at least make them turn out better, especially for people they care about.
That's all I have for now.