People say that SJs feel a "need to belong" to a group more than other types.
I would think this would be kind of an internal struggle for ISJs, because of their Introversion. (Let me know if you disagree with that.) They feel uncomfortable in crowds, but they like to be part of a group. I guess things like this forum might be a nice combination for them, with personal space and group activity?
To ISJs, are you aware of a "need to belong?" Do you belong to organizations, clubs, groups, etc? You don't have to say what they are if you don't want to.