While I can understand the nervousness about a price dump after the expansion, and am not planning on selling myself, there are several issues with this:
The negative perception it will create of us having a stable/valuecoin that we have to “artificially” keep at peg by banning selling, even temporarily.
Many people have legitimate reasons to sell. For example, selling half their ARTH rewards for DAI to deposit as LP.
The aim of the expansion to 20mn MC was to make the system more robust. Either this has worked or it has not. If we go into contraction, then that is what the market wants. We have other intrinsic (arth to arthb) and AIP (penalties and incentives) mechanisms that will help move the price back towards expansion. We cannot always be expanding, and rewards are available in either type of epoch.