The Discourse team rolled out a change intended to help with performance, which automatically closes public threads that are larger than a certain size. The Guns of Infinity topic was locked for this reason.
When moderators or administrators try to re-open the topic, it just re-locks itself.
We’re dealing with a few bugs in Discourse here; Discourse Support has said that they’re working on it/investigating.
Discourse Support tells us that the limit is really 10,000 posts, even though the message says “200.” They’ve apparently fixed that error in an upcoming build of Discourse.
Discourse provides an option to change the “auto close messages post count” limit, but it doesn’t work. Discourse Support says that @sam_saffron will investigate. (Go Sam!)
a) Discourse says that the limit can be disabled by setting it to 0, but I tried that, and it still re-auto-locked the Guns topic.
b) I also tried setting it to 20,000,000 posts, and it incorrectly said that the Guns topic had more than 20M posts, which is not true yet.
The reason they’re trying to cap topic size is explained in a topic on the Discourse Meta forum. Discourse Support explained to us that it’s a big performance problem for them to handle so many posts in a single topic, that it makes the topic unusably slow on mobile, and they plan to fix that “long term” but not right away.
(I dunno. The Guns topic looks fine for me on my iPhone 6S ¯\_(ツ)_/¯ )
That’s all the news we have right now. Hold tight!
Honestly, I think huge threads are causing performance issues because Discourse uses the endless-scrolling system. If threads were split into pages, with each page limited to X many posts but no limit on posts per thread, it would be fine.