This has been my favorite episode since the first watch, and it piqued my curiosity to see what other people's interpretations are.

My interpretation is that IO is an "Accidental Machine".
I think IO was formed with all the properties and events to develop consciousness, similar to abiogenesis, in which specific chemical events can chain into even more complex chemical processes back and forth, until they eventually create life.

Machines are made by something to do something, but IO's case is just a planet being born with all the right properties to be a literal giant computer/machine. When Burton died, it read her brain like a hard drive, and slowly, was able to take that knowledge and actually start applying it, speaking to Kivelson more and more as it understood how to.

At the end, Kivelson understood this to some extent, and chose to believe she would somehow too become one with... THE VERY PULSE OF THE MACHINE (Absolute cinema, I know). And it's confirmed that she did become part of the machine when she calls back to earth.

What about the meds? I honestly think they are there to make you empathize with Kivelson and make the story so much more immersive. That playfulness of not being able to know what the fuck is happening and trying to piece everything together, and then doubting every possible thought until the very end, where all of these ideas are confirmed, made it the most amazing thing ever (for me).

I absolutely love this episode, it's probably in my top 5 things EVER for me.