Reached +999 Itani faction last night and I've stopped receiving the "faction increase" messages as well. I have no idea if that is normal, just adding to the data.

Yes, that's normal. People have reached +999, done trading for a whole day, and nothing. Like I said, it has always been thus, except for that UI beta thing. Apart from that POS, Joyce has had +999 on everything but Serco (for RP purposes she keeps neutral) for the longest time, so I know what I'm talking about. It seems it's an exponential curve, and the points you get by then are so reduced you don't even get an "increased slightly" message, because you do not earn anything close to one tenth of a point. Bots, for example, give you either .45 or .75 of a point (I forger which, ask Solra or yoda) and thus you do get "slightly"; with +999 faction and trade, maybe you get 1/100th of that, but I suspect not even that much.

The best way to get POS was back in 1.0.x when you could get standing for killing enemies in a NFZ. So if I'm Itani and I kill a Serco inside Itani space, I'd get Itani standing. That's how I got my POS, which I kept until I lost it due to a fraking Escort Mission three weeks ago. Blah.

I am POS with UIT, and at no point did i stop getting "standing increased slightly" messages.