While statements which have a negative connotation are prohibited, this would not apply where the listener can be expected to understand that nothing derogatory was intended.
Therefore, halachah permits making an ambiguous statement if:
(1) Nothing derogatory is intended; and
(2) The unintended meaning of the statement is only mildly derogatory; and
(3) The statement is made in the presence of three people or in the presence of the person being discussed.
As an illustration, the early commentators offer the statement, “In that house, something is always cooking on the stove.” This could mean that this family’s door is always open to guest, or it can mean that the family is overindulgent. If the statements were to be made in the presence of three, one can safely assume that it would eventually become known to the family of whom it was said. Such being the case, the listeners would assume that the speaker intended it as a compliment. It would also be permissible to make such a statement in the presence of the family of whom it is said, since it would be obvious to all that there was no derogatory intent.
Sefer Chofetz Chaim, 13 Tishrei, page 74