>>1392566So.y as I remember was replaced ariubnd the time when s.oylent was introduced. At that time it became more and more known that it has high estrogen content. Therefore it became associated with being effeminate, weak and spammed. That is where the so.yjak and "s.oiboi" come from.
This became annoying after a while so it was filtered.
Sometimes there is no apparent reason and it just done for fun or because they feel like it, like the often used
t.bh getting changed into "desu", which is cute but I don't see an exact reason for that.
