Great point! My pH is also 8.2. I have not tested KH but I do know my water is very hard.
My tap water actually comes out at just under 7 and in 24hrs it is 8.2
My question is if your not messing around with your water why would you have to bring up the KH ? What could cause ph fluctuations at a low KH if you are doing your do dillegents and proper husbandry?
If your KH is low you are more prone to osmotic shock. If your TDS is low and/or unchanging it is less dangerous. PH swings don't kill fish though. KH is the buffering capacity, that is to say the lower your KH the more your water has the ability to fluctuate ph. I'm not an expert though. PH and tds (the thing that kills in osmotic shock) are linked.