I have compared it to sometimes losing my "integrity" (since if I believe something to be true and the other side NOT to be true, then how can I possibly say, "We're both right" or allow the wrong side to pretend it's right?) ... but I like your comment better. The compromise does feel at some level as a "loss of self."
Yup, I don't think it's about integrity exactly...
In my previous relationships, short as they were, there was something about other types that went beyond "agreeing to disagree" - compromise to them implied that I needed to actually give credence to the disagreements, to change who I am, rather than just see the outside problem as a problem that needed to be negotiated to both party's satisfaction.
There was also the tendency for expectations be unfair - ie: I want to spend every moment with you and I'm upset that you are working overtime... oh, you better get that raise or I'm going to crush your soul. Those kinds of traps are poison for NTs, if they realise it or not.
Both of us are pragmatic in my current relationship (INTJ). Using the same example, we had an issue with time spent with each other. In previous cases, the non-NT would somehow imply that they had to change us/the NT had to change for the problem to be solved. In the NT-NT relationship, it was assumed that the problem was a given and that we needed to resolve it - in other words, it wasn't that she or I needed to change who we are - the resolution rested on finding a way to increase time spent, quality spent or any other factor that would lead to a feeling of 'not spending enough time together'. In our case, the issue had to do with quality, not time.
The end result was a schedule change, so that we both get longer periods of work time rather than this constant abrupt changes that make 'together time' confusing and less meaningful. Is that a compromise? It's not to my GF and I.
The result is often the same, but the approach is significantly different. The only times we use the word compromise outside of the NT 'definition' is when expectations don't match up with reality. In those cases, the other person is expected to explain why it isn't reasonable and get them back on track for the other person to start the trading process. The only problems that can be resolved are ones that don't touch that 'core' part of the NT.
I wonder if that makes any sense...