you're right, I should have said that "man made gain of function viruses-that-infect-humans are quite common in research and many times moreso than random mutation zoonotic species-jumping viruses are in nature"
"Gain of function research seems valuable"...
and then I will note that I must have scored a point in that sentence even as I wrote it, because the next thing you do is hurry to defend gain-of-function research. I wasn't attacking it, I was simply pointing out that the public is not aware how prevalent it is in urban virology centers in their own cities. I'm a sciency type, I like research, but I'm sure the average Joe would take a much dimmer view.
"This gains plausibility from the fact that it wouldn’t be readily distinguishable from a natural virus, as it would just be a combination of the two genomes. However this is exactly why we can’t say for certain either way whether the source is natural or not - they’d be indistinguishable genetically."
you really need to read the Yuri Deigin page I linked: for exactly the reason you cite, it actually is plausibly readily distinguishable as man-made because the bats and the pangolin viruses that were spliced together don't occur in the same geographic areas and the Wuhan lab published papers about them before their more recent info was wiped from view, and in nature the likelihood of such a clean crisp (CRISPR!) gene splice would be astronomically the worst luck ever as a mutation, but quite likely for exactly the research goals you defend above.
"It is more likely on the face of it that evolutionary pressure on the virus to spread and the natural process of mutation and selection caused the mutations in question, simply because of the volume of natural mutations versus artificial mutations."
again, nope, artificial splicing (not mutation) is quite common and becoming much moreso as the cost of doing it has dropped within reach (something like $100K IIRC) of just about anybody. Natural mutations that follow the path of precisely covid-19's genetics, quite uncommon.
Read the Yuri Deigin piece, listen to the youtube. If you're in too big a hurry, skip the first 25% of each and jump in later, still completely clear to grok.