Trying to be both a platform and a community are goals which are often in conflict, especially in terms of operations. Communities really need things like trust

Trying to be both a platform and a community are goals which are often in conflict, especially in terms of operations. Communities really need things like trust, reputation, moderation, rules, and enforcement. These are things that are hard to enforce programmatically, and often require a lot of customization. e.g. reddit started as a platform for communities, but the success of /r/all made it more a community of communities, at which point some of the more extreme communities became a liability and had to be censored. In contrast, imgur appears to have managed the separation between the two quite well. It is still unclear what twitter wants to be.