One who conveys information to others has no control over who will hear it and in what setting it will be repeated. Whatever one says concerning another person may very well be repeated in the presence of that person.
It is therefore forbidden to say anything about a person that might embarrass him if it were to be repeated in his presence, even if the information is not derogatory.
It is forbidden to relate that an individual is a baal teshuah if the person is sensitive about this fact. This is true even in a community even where baalei teshuvah are highly respected.
Sefer Chofetz Chaim, 19 Tishrei, page 86