This was our only Director call during the week in Pula, and I think it has some interesting aspects. I was North, playing with a non-regular partner in the Butler pairs. At the table West bid 2♥ over partners 2♥. When I told her that this was insufficient she immediately replaced 2♥ with 3♥. I then called the TD, partly because I considered accepting and bidding 3♥ over 2♥. When the TD arrived he started by giving me the option of accepting, but during the time this took I had realized that I did not have a 3♥ bid (partner had passed initially, and although I never asked about the unalerted 2♥ it looked like it could be natural and we were vulnerable...). I refused to accept and the TD then took West away from the table, presumably to ask about the meaning of 2♥ and 3♥ (and possibly other calls). I don't know what was told to the TD, but when they came back he said West could bid 3♥ instead of the insufficient 2♥! The bidding continued undisturbed 3♥ - 3♠, 4♠ all pass. 4♠ made an overtrick, for a score of -1 IMP for us.
The TD's in Pula are generally very good, but this ruling seemed strange to me. We did not appeal, but I wondered what other people think (as a sidenote; I have several times been a member of appeal committees in Pula).
It also made me think about a slightly different scenario. Assuming a double by West is penalty and showing at least 4 hearts, would a double be a Comparable call? To me it seems to comply with §23A2 "Defines a subset of the possible meanings attributable to the withdrawn call" (or possibly §23A1) in that it also shows hearts, possibly a better suit than 2♥. If a penalty double is considered a Comparable call it may lead to another problem. Here 2♥X is no disaster (-500 would be a good score for N/S), but if North had less support he would probably like to accept the insufficient bid if he knew that it could be changed to a penalty double. Should he be informed about this before he makes a choice or is §23C (later adjustment due to damage to non-offending side) relevant?