Before I actually make my suggestion / request for an improvement, let me just say that I realize it would entail work and an acceptance of responsibility that may not be reasonable or practicable.
There have been several times that I wanted to send a response to a post to one person only. This was for a variety of reasons including:
b) The other poster made a mistake in quoting a sefer, rav, halocha, etc. that it would have been embarrassing to have publicly pointed out, but that the person would want corrected in a bitzina manner.
c) I had cautionary information that I feel would be helpful to a poster, but care must be taken that it is relayed in a mutar manner (and not be oiver loshon horo). In such cases you can let the teller know that the info will be viewed by three people who know who I am, and possibly require that the teller or someone on your side verifies that it is truly permitted.
e) The subject of an unreasonable attack can be told that the attacker may not have a rational perspective about an issue, so not to take it personally or bother responding. In such a case it would be better not to let the attacker know that such info is being given.