Abba, I understand that you were trying to help Lavendar. The basic idea that you were trying to convey was a good and constructive one. But I
think that according to Halacha (as per the above sources) it should have been phrased slightly differently:
1. You stated it as a fact (that he had commitment problems). This is not a fact; it is merely a possibility and should have been stated as a possibility (if mentioned at all).
2. You concluded that he must have been dating not for marriage. There was no basis for such an assumption whatsoever. While the fact that he broke up with her could possibly demostrate commitment issues, there is no basis for assuming that he was dating not for marriage purposes, and that is a very bad thing to assume or say about someone.
3. Even when L”H is allowed for constructive purposes, one of the conditions (as stated above) is that there is NO other way to accomplish the same thing. In this case, there were other ways to do so. In my post to Lavender, I mentioned many possibilities for his actions while attempting to paint the least negative picture of the boy possible.
While I mentioned that his breaking up with her was probably about him and not about her, I made sure to: a) make it clear that I don’t know & b) make it clear that this doesn’t necessarily reflect negatively on him either, as there can be many reasons for his behavior.