There are a couple issues common to all the Backward Looking Functions. The first concerns whether a person can respond to themselves. Although this is rare, speakers sometimes answer their own questions as shown below or reject/accept their own utterances. In the example below, u answers her own question (``will I be able to take the tanker plus four boxcars'') and then goes on to ask another (``I need two right'').
utt1: u: <sil> I guess <sil> with one engine <sil>
will I be able to take the tanker <sil> plus four boxcars <sil>
utt2: u: no
utt3: u: I + need <sil> two right +
Another issue concerns acknowledgments. Utterances such as utt2 are clearly acknowledging understanding/hearing what the previous speaker said. It is a difficult issue whether utt2 is accepting utt1. If you do decide that utt2 is an accept or an accept with uncertainty, you still need to mark it as an acknowledgment since acceptances by their definition indicate acknowledgment.
utt1 u: um engine two from Elmira to Corning utt2 s: okay utt3 s: let's pick up oranges in Corning