1. The whole newfags thing. So what if someone is new to a community? Everyone is at some point, welcome them in and ignore them if they are toxic. It really is sad that people grasp at self importance and feel some sort of false superiority by being in a certain community longer than someone else. That person you are feeling so superior to and insulting because they are new, they are just going to ignore you, I doubt they are impressed.
2. Not recognizing the meme. Consider the massive amounts of cultures, genres, communities, languages, countries, races and social groups, and within them the large amount of sub groups, all of witch you are not part of and will never recognize or even understand the "memes" or inside jokes. I am sure to you it does not matter, so why does it matter for them? It doesn't.