Personally, I'm just going to go with T for now. I think I type as ISFP sometimes because I "indulge" a bit in that side of myself. I don't think I go as far as ISFPs though.. (and I don't think they're inferior for being more F either btw. I'm a little envious. It seems to come easier for them.).
Secondly, a lot of my emotions are intense and negative to boot. I read this about ISTPs and it's more like me:
An ISTP who is over-stressed may exhibit rash emotional outbursts of anger, or on the other extreme may be overwhelmed by emotions and feelings which they feel compelled to share with people (often inappropriately). An ISTP who is down on themself will foray into the world of value judgments - a place which is not natural for the ISTP - and judge themself by their inability to perform some task. They will then approach the task in a grim emotional state, expecting the worst.
ISTps have difficulty in controlling their emotions. When they do loose control, they may become biting, rough and excited, raising their voice and gesticulating fervently.
But because they need such a lot of flexibility to be as spontaneous as they feel they must be, they tend to become as inflexible as the most rigid J when someone seems to be threatening their lifestyle (although they usually respond with a classic SP rage which is yet another vivid contrast to their "dormant," impassive, detached mode).
I'm beginning to think that even INTJs and ISTJs have better grasp of F than I do.
To try to stay relevant to the thread, do any ISFPs just... feel the same as those above descriptions sometimes? I wonder how much overlap there is with the two types. I can be a nice person, but I'd feel like a fraud if I don't own up to the angrier side. I'm no saint. I wish I was. Same goes with being overwhelmed by positive feelings. I might be a little too open and intense if it gets the best of me.