Quoted By:
Reddit's algorithm shows you what most people have liked first, so spending time there makes you constantly exposed to stuff that goes along the ideas of other redditors. On the long term, this makes your humor, knowledge and political opinions align with the average's redditor, and the most popular posts/comments are the ones everyone likes, which reduces the range of discourse a lot, even when you go on smaller subreddits.
Reddit litterally trains its users to laugh at certain things, expect certain answers and like certain memes.
We don't really care about reddit but many people here can tell when they see it, such as in this thread, and whenever redditors find a certain 4chan meme/board cool it oftens gets overused to death or ruined with terrible, terrible posts from people who expect to be welcome everywhere because they were on reddit.
Hope thats sums it up well, and please stop those 'what's wrong with reddit threads'