So a couple of things i remember from back in the old structural bioinformatics days...

Firstly, there are naturally occurring mixed-chirality (alternating) peptides. They are usually circular iirc.

Secondly, no you can't really have larger proteins with both left and right (ignoring glycine). They would not fold into nice helix/sheet strucures and likely just be random coil.

For cells to have mixed populations of all-L and all-R proteins would mean doubling up all the machinery for creating them.

One theory that I thought was reasonable for why there's a monochiral world is that once the arbitrary choice is made (L or R) then that gets 'locked in' by all the machinery around that choice. As in, L 'won'.

My initial hypothesis is that there's something present in the early stages of life that has a higher energy state making it unsustainable for use in a certain conformation and so it was nearly immediately selected out.

E.g. a ring structure whose substituents are affected by steric hindrance in the left-handed scheme.

And the path of least resistance was just to adapt and build around it. Once that precedence was set everything became as such. I expect in the earliest stages of life this would have been an immense factor as metabolism was not nearly as sophisticated as we know it today.

And this selective process may have ocurred well before anything we have observed/modeled, and may well be erased. Which is to say I agree, but with the caveat that it was a substrate-dependent mechanism which selected the downstream components rather than random chance.

>> One theory that I thought was reasonable for why there's a monochiral world is that once the arbitrary choice is made (L or R) then that gets 'locked in' by all the machinery around that choice. As in, L 'won'.

This seems obviously true to me. Mixed doesn't work, so as molecules and systems of molecules started replicating one chirality won out. It's just chance and there's nothing magical about the chirality "chosen" by the process.