I'm going to start searching those forums then

Found two new codes so far:
Shroom post in “Wall Jump” - 2093217clue3
Xero’s post in “What is normal?” - 5419213you’re34
I'm sure there are more, I'm basically searching the first 3 pages of every active front page topic in unlocked forums.
So far none of the codes we've picked up seems to give a clue towards specific threads so this is all I can do for now. I'm really interested by the numbers at the end of the words, though.
EDIT: Will update this post with any new found codes.
7823521smart55 - SMIC in Temple of Heart story topic
3865989too13 - KS in the ludum dare programming topic
8330622here8 - SK in the super star hereos other games topic
6306640if21 - CY in the Super Smash Bros nintendo topic
5334982a2 - Nan in the art contest RO topic
3890448in5 - Shroom in a speedrun records C1 LL topic
6314402There1 - Kab in the LL chapter 1 release news topic
Right, I have all the thread codes, time to order them from smallest to largest!

6314402There1, 3562350is1, 5334982a2, 2093217clue3, 3890448in5, 8330622here8, 3865989too13, 6306640if21, 5419213you’re34, 7823521smart55
We know it forms a sentence: "There is a clue in here too if you're smart". Tbh I personally think it means there's a clue in these numbers, referring to what Doram said - that two puzzles point at themselves for the answer..
This is starting to feel like an IQ test lol.