There is no reason srikethrough shouldn’t be a core feature of markdown. There is nothing to discuss. Every markdown implementation that implements srikethrough, does it the same way. When (not if) you add srikethrough to the standard, you are going to specify that two tildes get parsed into a <del>; anything else would be unwise.
- there is minimal extra cost involved in adding srikethrough to the standard now.
- by delaying to add it, you gain nothing.
- by adding it you would make a lot of people happy.
- what exactly is your problem here?