A lot of the responses to this thread have made a lot of great points. Some things I agree with, others I don't and I don't have a solid answer to the problem around cliques (There may not ever be one), but I don't believe curbing peoples creativity and freedom to shape their factions as they choose is an answer that benefits this community.
I 100% would love to see the community open itself up to being more inclusive of others and less prone to hosting its social circles/cliques, but as others have pointed out this is a social aspect that is unavoidable and I myself have been guilty of keeping close to the social circle I've felt safe/comfortable in due to bad past experiences.
As has been said above somewhere, there's nothing wrong with having a social group that you're most comfortable with, but the best thing is to try to consider others, especially those newer members to the community, so we don't become non-inclusive and a negative presence to the overall community.
I don't have any real opinion that goes beyond the one faction I'm active in right now, but my views are entirely personal and shaped by the consequences of cliques and that whole "Them vs Us" mentality. At the end of the day, I want to see people come together and enjoy themselves, but I don't believe sub-factions are the only cause of cliques, nor is removing them the answer to improving the issue in my opinion. Be creative. Write and let come what may. But above all else, be kind and respectful in all OOC aspects where absolutely possible.