Again this makes the assumption these are questions.
"...Over time, mutations at other genes ("modifier loci") evolved to restore symmetry, while maintaining insecticide resistance. The developmental system adjusted to the necessity of carrying the mutation conferring insecticide resistance."
Who knows what the genetics were. The usual explanation is that there are naturally resistant members present, who under the regime of insecticide merely replaced the population. So the insecticide acted as a selective factor, eliminating the non-resistant.
What I was trying to theorize was a lot more general (and perhaps empty) which was how the evolution of body symmetry is an expression of evolution in a gravitational field. Once these general forms and their symmetries were established, their maintenance was highly conservative, have persisted in time and range over a broad spectrum of plants and animals. These observations about conservation of general form indicate the presence of a highly stable environmental constant.
"It is advantageous to be a mirror. But then this rings in the problem of inorganic life. Why are particles symmetrical? (am I with you?)."
First, remember that an advantageous adaptation doesn't explain its origin, only its persistence. The larger point was to show how evolution of form doesn't require genetic or biological creation out of nothing. Gravity is a given, so the question is what is biological evolution doing in relation to that given.
As for atomic and molecular configurations, these have spatial symmetries because of their electron arrangements. These arrangements follow a physical principle of tending to the most stable configuration available--whatever that is. In general, stability is defined as the minimization of potential energy (everything balances).
"Perhaps biology and physics are secretly collaborating, a symbiotic relationship. If like struggles to be geometrical, then this could be read as life imitating physics. So the question isn't a genetic one. It's a cosmological one."
Remember that physical principles are abstract descriptions of physical conditions. So living processes and organisms don't struggle with physics, they express physics. There is no collaboration.
The more general point is that life doesn't struggle to be anything. So, symmetric body shapes are not a struggle with gravity, but merely follow as a consequence of evolving within such a physical system. This relieves some part of biological evolution of a telos of design.
But I should add what I presented was completely theoretical. It is something I cooked up while working on unrelated gravity studies. There are a lot of problems with it. The basic idea grew out of arguments and discussions over how organisms orient themselves in space, which is a whole other problem.
Chuck Grimes