The openness in pouring out emotion in email to other people is not very IxFP though, as feelings and emotion are generally not expressed directly on any regular basis. Looking for constant feedback is not very IxFP either, as the the type is said to show an almost extreme indifference to it.
I think Naranjo connected unhealthy e4 to BPD. Enneagram is more about unhealthy fixations & mentalities than Jungian type/MBTI which is more about cognitive preferences (not necessarily healthy or unhealthy). Because of the way tests are written, depressed & unhealthy people may type INFP when they are not. If these people recover, they may find they are not INFP. This has happened on these forums & elsewhere.
Fi is actually rational for an INFP though, so equating this kind of emotional reacting to Fi is a misunderstanding of it. Under severe stress or depression, all personalities can become distorted so that it's hard to tell what preference they were to begin with.