If you have a personality disorder, your patterns of thinking, feeling and behaving are more difficult to change and you will have a more limited range of emotions, attitudes and behaviours with which to cope with everyday life. This can make things difficult for you or for other people.
If you have a personality disorder, you may find that your beliefs and attitudes are different from most other people’s. They may find your behaviour unusual or unexpected, and may find it difficult to spend time with you. This, of course, can make you feel very hurt and insecure; you may end up avoiding the company of others.
The diagnosis applies if you have personality difficulties which affect all aspects of your life, all the time, and make life difficult for you and for those around you. The diagnosis does not include personality changes caused by a life event such as a sudden traumatic incident, or physical injury.
... From Mind. More information here.
I don't think posters are misunderstanding, fluffy. It is extremely difficult to maintain healthy relationships with people whose mental & emotional processes are unusually rigid, particularly when the partner under discussion has no diagnosis and the poster has been trying to get them to see reason in ways that the partner simply cannot do.
You don't say what type of PD you have, but you should be sufficiently well informed on the subject to appreciate that no-one here says "All PD sufferers are bad people". There is, however, no law saying that people have got to live with anyone they find abnormally difficult, whether or not that person has a mental health condition. Considering whether their partner might have such a condition can help them make that choice, having accepted the partner's unable to change significantly.