I think that some of the disagreement here comes from a number of different people from different countries applying different sets of regulations.
I have no idea what the regulations are governing the logging of instrument time and night time in the UK, Australia and France, and I wouldn't presume to tell anyone from there what it correct under their regulations. I do, however know that the regulations are in the US, and misd-agin is correct for the US, Under the FAA regulations you may *only* log instrument time when the conditions actual or simulated, would prevent adequate control of the airplane using. Misd-agin quoted the relevant regulation governing this:
FAR 61.51
(g) Logging instrument flight time. (1) A person may log instrument time only for that flight time when the person operates the aircraft solely by reference to instruments under actual or simulated instrument flight conditions.
The intent is pretty clear, but in case someone is tempted to try to quibble about the meaning of "actual instrument flight conditions", a legal interpretation by the FAA's Chief Legal Counsel clarifies exactly what is meant by that :
"Actual" instrument flight conditions occur when some outside conditions make it necessary for the pilot to use the aircraft instruments in order to maintain adequate control over the aircraft.
So, if you were able to keep the airplane right side up by looking out the window, as you can in clear conditions above a solid cloud layer, you are not entitled to log instrument time under US regulations. Perhaps other countries' regulations are different.
Also, for the US, logging of night time is not sunset to sunrise, it is from the end of evening civil twilight to the beginning of morning civil twilight. Granted, the original question about night time was from someone in France and the EASA regulations may say something different.