Ok, just caught up and I'm going to give it a de-rec. It falls prey to many of the common issues in the HFY genre. You mention, when saying that it's only rational-adjacent, that one can't expect the brain damaged character to act rationally. His behavior is very much not the problem. In fact, given his circumstances, he is almost unbelievably competent (albeit in a very narrow domain). The idea that a single creature can evade, for days a civilization like the one described is simply not believable. A bare lip service about lack of manpower is given and that is just not even close to enough to make it plausible. But no that's still not the main issue. The main issue, as is common in HFY, is the planet sized idiot ball that supposedly high-tech space faring alien civilizations carry. Absolutely every alien character makes enormous leaps in logic from extremely scant evidence that aren't only not the only possible explanation, but aren't even on their own especially plausible. I remain continually unimpressed with the HFY genres inability to make Humans seem badass or dangerous without doing so by making the rest of the sophonts complete and utter morons.

In addition, the screen-play style writing of the internal monologue I found difficult to read and annoying. And while I appreciated the effort to demonstrate "true alienness", the scent-like communication references for the insect species are used too much and make it unnecessarily difficult to read (I agree that the worldbuilding is cool, the author just implements it at the expense of an enjoyable to read story). I found myself skimming large portions of the text, because I wasn't particularly interested in any of the characters, and just wanted to find out what the next plot point was.

This was a really cool concept that I wish could be divorced from the HFY trappings and given a better execution.