QuoteThe MSSR provides an incentive to both traders and shorters to work towards that goal:

    For the owner of the short position, the MSSR is a penalty. This encourages him to always provide sufficient collateral.
    For the trader, the MSSR is an incentive to sell bitUSD, because the margin call pays more than the settlement price.

Everything is vise versa actually. MSSR protects the owner of short position, since it puts a limit on a price at which the borrowed asset is bought back when margin call is triggered. For the trader this limit is not good, because it does not allow to sell at better price.

Like I promised, I posted an example about margin calls on steemit: https://steemit.com/bitshares/@cyrano/how-bitshares-protects-mpas-using-margin-calls