Added description about limits

bsip-0042.md

@@ -57,6 +57,14 @@ correct direction, the price should move towards par. If the price moved too
 little, we adjust more; if the price moved too much, we adjust less. Finally
 this will lead to a stable result.
 
+We may consider setting a hard limit on the offset which may make us feel safer.
+Actually, to be safe, we do need to start with a small offset, and adjust little
+by little. Since it's expected that the best offset will be figured out by the
+negative feedback mechanism, a preset limit may impact the mechanism negatively.
+A few witnesses publishing too far away offset doesn't harm much because
+they won't move the median much. In addition, stake holders may vote down
+perceived bad actors.
+
 ### Risks
 
 All the adjustments (price feed, or MCR, or MSSR) in a downtrend actually looses
@@ -129,13 +137,22 @@ When witness publishing a price feed, after got price of BTS from exchanges
 (assuming it's `P`), check trading price of the publishing SmartCoin,
 adjust `P` with an algorithm.
 
+To be safe, the algorithm should start with a small offset, or a value near
+the median, and adjust the offset little by little.
+
 The algorithm should implement negative feedback,
 that said, it should track historical adjustments and historical differences
 on trading prices of SmartCoins, and make new adjustments accordingly.
 
-We don't force all witnesses to use same algorithm, instead, witnesses are
+We don't force all witnesses to use a same algorithm, instead, witnesses are
 encouraged to implement different algorithms for same goal.
 
+We also don't set a hard limit about how much the offset should be within, in
+order to let the negative feed back mechasim find the best result by itself.
+Witnesses should make their own decisions on whether to set a hard limit and
+how much should it be if need to set one, generally, to reduce impacts caused
+by bugs.
+
 # Discussion
 
 [To be added]