One may no mention that someone is a baal teshuvah if either the speaker or the listener considers this derogatory (which, in fact, it is not). Based on the prohibition against relating negative information or information that could cause harm or hurt, it is permissible to relate that a person is a baal teshuvah only if, in addition to the speaker and the listener not considering this to be derogatory, the baal teshuvah himself is open about his past and if this fact were mentioned in his presence he would not feel hurt; or (in the case where the baal teshuvah is sensitive about his past) the listener is known to be discreet and the information will never be passed on to others.

Sefer Chofetz Chaim, 20 Tishrei, page 88

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