I belong to a small, open community that meets in person and is largely run by consensus. (There is an organizational authority who can step in if something really requires that, but said person is reluctant to do so. We're all adults and presumed to be able to solve our own problems.) Most members get along well, but we have one who lacks basic social awareness and has no filters. This member tends to make inappropriate outbursts during gatherings, talk over people, and otherwise be a source of minor but frequent disruption. No single incident has been major enough to prompt action. Because this person is difficult, nobody else wants to have a private conversation with him about this. It seems that he is aware of the problem, because when his wife joins him we see her correcting him and he is better for a while. But she's not there all the time.
If this were an online community, we would be able to avail ourselves of an "ignore" button. (Also, problem posts could be deleted.) If he did something that was clearly and majorly out of line, we could get the authority to step in and strongly encourage him to take a break for a while. (It's not clear that an actual ban is possible, unless of course he were to become a safety threat.) So we do our best to ignore his bad behavior the old-fashioned way, but it wears on people.
The group is informal in structure; there are no officers or policy discussions or the like. I don't think "get everybody but him together to talk about the problem" is a viable strategy; that would feel too sneaky to many members. Whatever we do in response to this behavior will have to be more organic. Because the community tries to be open and welcoming, fixing the problem (or learning to ignore it) would be preferable to driving the member out.
What strategies can individual members of our community use to reduce the disruptive influence of this member?