>>7785780I'll explain because maybe you're new. Threads in 4chan have two (2) limits.
(1) Image limit: When a thread hits image limit no more images can be posted in that particular thread. Only text replies are allowed from that point forward. The discussion can continue, but no more images can be posted.
(2) Bump limit: When a thread hits a certain amount of replies (total), the thread no longer "bumps" (goes, jumps) to the first page of the board whenever a reply is posted. That includes image replies.
So, replying in this thread with either images or text will not "bump" the thread to earlier pages.
Users more often than not "find" or decide to participate in threads that are in Page 1, maybe 2, and if interested will go to a thread in 5 or 6 to see what it is about. If you see in the Catalog a thread in page 8-10 with the bump limit reached you usually consider that a "dead" thread. Since no anons tend to visit it at all and they refrain from posting.
A new thread permits this one to die, and encourages other anons to post in the most recent iteration because it's "alive" and continuing to bring interested anons to it.
TL,DR: Anons are less likely to reply to a thread after bump limit is reached. A new thread keeps the topic alive and new anons interested.
