Shalom to all,
I am wondering if anyone can shed some light on the following issue:
In Keses Ha'sofer 8,5 a scenario is discussed in which one wrote a rei"sh and subsequently changed it into a dale"d by adding an akev on the back etc. He concludes, that although one is not required to erase the whole thing, rather one can erase the akev together with one of the two limbs of the rei"sh, nonetheless "hamachmir... tavo alav beracha".
My understanding of this is: that since there are opinions (i.e. Rada"ch) who would deem it "miktzas ha'os be'chak tochos" to erase only some and leave some to be included in the final letter, therefore, there is virtue, albeit not required, to erase the entire letter before rewriting it.
Now, just 3seif'im later, regarding "me"m pesucha shenistema" Keses rules, that although the me"m is written in two distinct parts (and therefore, only the latter part of the me"m is required to be erased and rewritten), nonetheless "yesh le'hachmir le'chatchila heicha de'efshar" to erase the me"m in its entirety before rewriting it.
So, here is my question: is it the same principle at work in both of these rulings? If so, is there a meaningful difference between the wording in seif 5: "hamachmir... tavo alav beracha" and the wording in seif 8: "yesh le'hachmir le'chatchila heicha de'efshar"? If there is no difference, why does the Keses need to state both rulings seperately? and if there is a difference, what exactly is this difference and by what virtue are the two scenarios different from one another?