Bug overview description.
Whenever I am logged in and my IP changes to one that is apparently banned, e621 logs me out and informs me that I am banned.
I believe this should count as a bug because the behavior is unexpected (a logged in, non-banned user does not expect to suddenly be logged out automatically).
I can still log in normally once my IP address changes away from the banned one.
What part(s) of the site page(s) are affected?
All
What is the expected behavior?
To remain logged in.
What actual behavior is given instead?
e621 logs me out.
Time of incident (if applicable).
Can you reproduce the bug every time?
No; only when my IP happens to be banned.
What steps did you take to replicate this bug?
In my case, simply using Tor Browser and being logged in, WITH "Enable roaming" checked. Eventually the exit node node happens to change to an IP that is banned.
I IMAGINE that this can also affect anyone whose ISP assigns them a non-constant IP address.
Errors or other messages returned (if any).
The "You are banned." banner

I thought TOR browsing of this site was what was banned.

Tor isn't supported, a large number of IPs from tor are banned.

Isp are alloted a certain amount of ip addresses by the local RIRs. So to make the most of it they prefer to use dynamic ip address to curve unused ones. The side effects is when a website try to block a user. it not blockng the user but the reuse of the IP on their servers.

Other words, you can get this error even without being on Tor.

We rarely do IP bans. IP bans are very unreliable, we use them as a last resort. Tor nodes tend to be ran on servers with static IPs.
I'm not saying it's because I suspect them to be using tor, it's because they specifically stated they are using it.
Tor nodes(specifically exits) are banned from the site which is why I stated it is unsupported.