Quick suggestion on this front: Associate tags by frequency of them being together on the same post, and drop the 2-tag max. Let a post be tagged #science, #biology, #biochemistry, #homelab, #pcr. Then, when tags appear to be used more often together, above some certain threshold, list them as associated on the #tag page, similar to the similar posts feature that was removed. That way, if I think #writing and #writebetterdammit should be related, I can always just use the community tag for relevant posts myself. Additionally, you could have a suggested tags field to quickly add commonly associated tags, though this might bias the algorithm in the long run... Only trouble would be that it could be abused, letting me associate #murderer and #yourmother if I'm feeling malicious...