A11ey, the login issue is a 3rd party cookie issue, i think. When using Chrome (that blocks 3rd party cookies by default because they are evil), I have to sign in every time I come to the community. When using edge, my work browser which isn't configured to block 3rd party cookies, I stay signed in consistently.
3rd party cookies are being blocked by Google in Chrome (65% of browser market share). Privacy minded customers already have or will be blocking 3rd party cookies. Smart domain admins will block them via policy. If the community relies on 3rd party cookies, this will always be broken and will only get worse as time goes on.
On a side note, i navigated deep into the reply tree to reply to this. I wasn't signed in, so when I hit the reply link, it prompted me to log in. At which point, it took me back to the top of the thread and I had to navigate all over again. This community is harder to use than the last one.