First, how do you see hypermindfulness playing out in a relationship? I can see a scenario where an INTP's spouse came up and was excited about something, and then the INTP squashed that excitement by maintaining their remove and analyzing the topic to death. But this seems more like a general problem than a romantic problem. What other issues does hypermindfulness create that are specific to the context of an intimate relationship? Another thought is that you might consider renaming "hypermindfulness"; hyper- usually implies overuse rather than poor use, which I think is what you're getting at here. Just a thought.
I do think of this concept in the category of over use, not poor use. Seen from the other side of the coin, we just don't know when to quit sometimes. Most personality types don't share our drive to observe/analyze, observe/analyze, observe/analyze. In the context of love, supporting the other person and feeling supported in return are essential elements of a long term relationship. If a spouse can't share his or her passions, if that sharing is closed off, then distance, resentment, and walls will result. These can easily grow, spreading the poison. Of course, this problem would also be pertinent to friendships and family relationships. In love, however, the hyperMindfulness problem can have much more catastrophic consequences.
How else does hyperMindfulness play out in love? By seeking to attach importance to everything. When every conversation, every emotion, every fight and bad mood potentially changes the INTP's entire view of the relationship (i.e., the "truth" of it), you create an impossible standard. Under that kind of pressure, nothing is going to last. It can't survive the scrutiny. Sooner or later, a series of events and observations are going to lead you to label the relationship as inadequate or erroneous, probably from the very beginning. You will rewrite your entire conceptualization of the relationship based on your progressive gathering of information.
Again, this level of mindfulness simply won't support a long term relationship. We need to learn to set mindfulness aside at times. We need to enjoy basic moments of existence and feelings. We need to use these later as evidence when our mindfulness returns and once again wants to label the relationship a lost cause. Bottom line, when you find yourself gathering a body of negative facts and judgments about your relationship, ask yourself, is this course going to make me happy? Is this course going to leave me better off? Try to put on the brakes now and again. INTPs are famous from moving from thing to thing, reaching a certain point of understanding, then moving on. We are wired to treat relationships the same way. But we have a choice. We just have to realize that we are empowered to make it.