CS - that AIC I mentioned specifically stated that VFR at night (even with no horizon) was not to be logged as IMC. The problem is that AIC's are really only some (unknown) persons opinion, and don't matter any more than your or my interpretation of the rules. Only if it came up in court, and a judge made a ruling, would we know for certain.
For instance: you have to log a certain minimum IMC for various licences, which you and I most probably achieved "under the hood". Is this legal IMC? As long as you are flying on instruments it is under the definition, and the definition doesn't actually state that you must not be able to see out of the window - the hood is just for the instructor to be statisfied that you are learning correctly.
The broadest interpretation would allow you to log IMC even in day VFR - provided you were looking at the instruments, and not out of the window.
If you log IMC for 90% of your flying and someone queried it - you could just pull out a pair of "foggles" from your navbag and tell them you wear those in flight for practice! (N.B. you would probably need a safety pilot here to satisfy the lookout requirements.)
This is just one of those things that has been around forever as too vaguely defined, but nobody cares enough to go through the process of cleaning up the regs. Add it to "When exactly can I log co-pilot time", and "How does my personal flying count towards my duty hours."