I keep hearing about people who used to play FAF a lot, but stopped for months to years, and would want to try playing again, but don't because they're now overrated at their old rating and don't want to have to lose so many games just to be able to play balanced games again. I think my above points are still quite relevant, and it would make sense for FAF to implement some sort of sigma increase over time.
For example, FAF could do an increase of 0.4 sigma per day for users with less than 150 sigma. That would equate to an increase of ~36 rating uncertainty per month with a max of 450 rating uncertainty. For perspective, most players with high game counts have between 150 and 300 rating uncertainty, while new players start with 1500 rating uncertainty. So, that would cap a regular player at losing a maximum of about 216 shown rating after roughly 6 months of inactivity, with no additional rating decay after that. Note that that would just change the uncertainty and not the base rating, so it would basically make the player a little more 'gray', and their base rating would consequently get adjusted a bit more quickly to match their current skill level, while their shown rating would temporarily be a little lower in the interim (since their rating is a bit more uncertain).
This will become irrelevant with the division system as the divisions reset after a certain amount of time.
Does division resetting increase sigma or have some material impact behind the scenes? Like, I understand that it then won't display someone's division until they play X more games or smth, but given that divisions largely seem like a cosmetic change that displays division instead of rating, that division reset sounds more like a cosmetic change that doesn't remove sigma relevance.
Regardless, this still has relevance for global rating either way.