Why are topics closed after 30 days? I’ve got a follow-up on a topic that has been closed, while that topic already is a follow-up. Opening a new topic for the same issue for a third time doesn’t feel right.
Does leaving a topic open more harm then having multiple topics? Same goes for GitHub btw. Never seen a project where so many issues are blocked.
It’s closed specifically for the purpose to prevent people bumping months old topics about issues that are no longer relevant in recent versions.
Support topics are for support, and are closed after one month of inactivity. At that point the original support query should indeed be handled. Topics in General, Development, etc are not closed automatically. If your topic is something not of the kind where you need help, it gets solved, case closed - you can use one of the non-Support categories.
On GitHub, issues are locked a year after they are closed. Anyone wanting to leave a “I have the same issue!” comment over a year after we actually solved it is definitely better off opening a new issue. (It’s not the same bug at that point.)
I know that ‘+1’- or ‘I’ve the same issue’-comments were a problem on GitHub, but from my experience (I’m a maintainer on some repos) this problem has been solved by GitHub’s Reactions.
I found a GitHub issue that has been closed as a ‘wontfix’, because it’s a ‘rare use case’. Why should that issue be locked? Things can change and what was a rare case back then, it can be an important feature right now. It’s all up to you, but in my experience duplicate issues (or no new issue with new information at all) are more annoying then having to remove some ‘+1’ comments sometimes.
Back to why I started this thread in the first place. I still have some problems with (USB) tethering. These topics are about the same issue:
This isn’t a support question, but a feature request. I’m not an Android developer, so I’m not sure if this is a problem that can’t be fixed because of some Android limitations. Can one of those topics be re-opened (not being a support question) so we can discuss this issue?
I don’t know the answer either, but if you think it’s a development discussion please feel free to open a topic in development or general. Your summary post above would do nicely as a thread starter. Your support questions were “answered” (but didn’t help/work) and didn’t get any followups, so I’m guessing not a lot of other people know the answer here.
Apparently because we decided we didn’t want to do it, and noone bothered to disagree for a year. At this point we might be at one of two states:
I don’t really agree. At least I think the issue locking and reactions address two entirely different annoyances. But we don’t need to agree on this point. You are free to choose your issue policy as we have ours. 
Well since you haven’t opened a new topic (yet), I’m just replying here (we may continue this elsewhere):
I just had a quick go on this - as I understand it, you want to sync between a computer and an android phone which are connected over USB in tethering mode?
If so, that was fairly straightforward for me. Tethering creates a local network which syncthing can natively use. Broadcasts (local discovery) works too, so I just fired up syncthing on both machines and they immediatly connected over the tethering connection. No magic involved.
We agree to disagree on the GitHub policy ;). No problem of cours.
Please re-open Sync using tethering connection (USB ethernet or Wi-Fi) as this is still relevant. I’ll comment in that topic
what’s more, why some topics aren’t closed?
i couldn’t identify the pattern.
disclaimer: i do love necro posting (obviously) and i completely disagree on every “auto topic closed” policy.
you should see how fossil-scm forums work! 
Only support topics are auto closed, and potentially there exist a few from many years back which predate that policy. Obviously some discussions can span over many years. Support requests are generally not those things.