I think it is true what you have stated in both of you posts, but my concern is that you have given as reason or causation for stasis (of the phenotype of a population) the exact same reason/cause that is true for change (of the phenotype). The cause as I think you may be stating it is Natural Selection. But I think the true cause is that the probability of achieving a beneficial mutation has been reduced to near zero in the case of stasis in an unchanging ecology; whereas in a new changed ecology a mutation surely has a higher chance of being beneficial compared to the other case.
You have in effect said, Natural Selection is the cause for staying the same and the cause for changing, I don't see the distinction that has to be drawn in order show what causes the one over the other event.
Edited by CosmicChimp, : clarity
Edited by CosmicChimp, : clarity, last edit