What is it about malleability that is such a big problem? In the almost 7 years of Bitcoin's existence, I am only aware of two "companies" that have claimed to have been negatively affected by malleability, and I believe both of them are/were lying (I know for sure that at least one of them is lying).
I would think that a more common sense fix to the sighashing "problem" would be to limit the number of SigOps allowed in a transaction, as I do not think there are many "business reasons" why any given transaction would ever need to have a large number of SigOps.
Malleability is an issue for off-chain scaling solutions such as the Lightning Network.
I understand that, but that is not how SegWit is being "sold" to Bitcoin users! What achow101 et al is saying is that SegWit is fixing his horrible malleability "problem" and will help Bitcoin scale with a defacto block size increase (via a discount in how much space SegWit signatures take up), but are leaving out the fact that LN/thunder cannot function without SegWit.