First of all, I'll note that Leishman is not a neutral third-party observer – he has ties to Core:

I think this is important to point out as a lot of people have given up on trying to understand the technical arguments and instead are relying on appeals to authority. Appeals to authority are much less effective when the authority is biased.

As far as addressing his arguments, I made an attempt to do so here:

And I've lightly edited these arguments and presented them again on SN here:

I am just a guy on the internet that wants to see Bitcoin succeed as sound money, which is why I'm pro-Knots. I have absolutely zero connection with anyone on either side. I am also a non-expert. I've tried to piece together what I can by reading, watching, and perhaps most importantly, thinking and writing.

The more I (think I) understand about the technical side, the more I have to assume that those experts who are basically saying "relax, this is a nothingburger" and trying to shove this change through have ulterior motives – such as Leishman above, or the main Q&A thread on SN, which conveniently doesn't mention the points I've made (to my knowledge – I haven't read the entire thing).