Plural of "presence"

What is the correct way to indicate multiple "presence"s in the sense of "I have a strong presence in this community"?

For example:

I have multiple online presence[s?].

It seems strange to me to use presence in this sense. Presence by its nature refers to the state of being present or proximal, and so you couldn't multiply be in this state. You are present or you are not present. So I would suggest

I have a presence in multiple online communities.

is actually what you want.

Even if you are referring to many people, presence still refers to a state, and ought to be singular

We have a demonstrable presence on English Language and Usage.

The use of presence in the online sense is new enough that you're not likely to find it in many dictionaries, but I can't think of any reason it wouldn't be considered a countable noun--you're talking about multiple discrete accounts with different services, rather than an overall amount of "presence." Presences it is.

Pluralizing "presence" in this way is the target of debate into schizophrenic-like cognition.

My presence spans multiple usernames, each of which are registered at several online communities.

That is a more-literal communication strategy, but reveals the awkwardness of relating with different people in different forums using different voice.

If not multiple usernames,

My online presence spans multiple web communities.