Gitter seems to be indexable by search engines. My experience using it as part of open projects has been mixed—the UI isn't great and the notification system is

Gitter seems to be indexable by search engines. My experience using it as part of open projects has been mixed—the UI isn't great and the notification system is, in my experience, unreliable—but if you're worried about your messages being discoverable, it might be up your alley.