A short update on my own experience with malic acid:
As I posted before, I had stopped taking the liposomal malic acid when I discovered that cooked and cooled potato starch was more effective at dealing with my ammonia issues (as I understand it, it gets turned into butyric acid by gut bacteria, and butyrate helps with ammonia). Since then, I seem to have developed some kind of reaction to potato starch, so I have had to return to malic acid.
Unlike before, I am now taking 14 mg of MK-4, a kind of vitamin k (this is a high dose). The MK-4 has changed my tolerance for number of things, including manganese and calcium, and I suspect it also increased my tolerance/need for malic acid, as earlier two sips of my liposomal malic acid gave me insomnia, whereas now it took maybe 10 sips in a day.
More recently, I have begun simply putting malic acid in pills ('0 size...maybe 300 mg?), and this seems to be working even better than the liposomal version. I believe someone else on this thread tried something like this before I did, also with success.
@kel88 Does your multivitamin contain B6 (pyridoxine, pyridoxal-5-phosphate, PLP)? You may have been saying this, but it seems like if there is B6 in your multivitamin, then it seems likely to me that the B6 is responsible for the "ammonia" symptoms from your multivitamin, not the methylfolate.