Chat to or chat with?

Short answer:

Well. . .

Why not follow the "crowd"?

Long(er) answer:

As long as chat to/with is concerned, chat with is way more common. This might get a little bit complicated and confusing, as I attempt to compare the patterns between the three closely related verbs. Note that pretty much 90% of the arguments here can also apply to chat.

So, for the benefit of doubt, let's take a look at ngrams about similar pairs:

• Speak to/with

• Talk to/with

How would I interpret this?
Chat has a bit of a more informal, more friendly overtone. The act of chatting is usually expected to be collaborative, two- or several-sided, voluntary etc. while there's less of this connotation in verbs talk and speak. In other words, we expect chatting to naturally be followed by with.

Pfft, Is that it?
No, there's more to it; let's use the irony of the name of "Quick & Dirty Tips" to quote one of their articles:

It’s true that the phrase “talk with someone” clearly refers to a two-way (or many-way) conversation. Still, “talk to someone” doesn’t rule out a two-way conversation. Any number of things could be happening while you’re “talking to” someone that you don’t mention, including that the person might be talking back to you. A Google search turns up many hits for strings like “I talked with them and they said”, but it also does for strings like “I talked to them and they said”, which indicates that many writers don’t interpret “talk to” to exclude a two-way conversation.

For the record,

1. “I talked with them and they said” returns 156k results from Google, while "“I talked to them and they said” returns 340k (!).

2. 10 results in Google books for "I talked to them and they said" vs. 1 result for "I talked with them and they said"

3. First 12 results in COCA are all talk to.

4. Almost all of the COCA results for chat to/with are using the preposition with.

5. Most of the consensus in an ELU question regarding speak to/with is about the bidirectional-ness of speak with; in a similar manner to talk with and chat with. However, no upvoted answer claimed there's an obligation in correspondence with choosing the pair related to the meaning implied.

The article goes on by bringing two of the Grice's Maxims as arguments, one for and one against the use of to.

The maxim of quantity

1. “Make your contribution as informative as required.”
2. “Don’t make your contribution more informative than is required.” - Grice's Maxims - Maxim of quantity

So, basically, since talk with is more correct; you should use that instead of talk to when referring to an interactive conversation.

The maxim of relevance/relation

“Be relevant.” - Grice's Maxims - Maxim of relation

So, basically, one could argue that talk to is better since the indication that the talk was interactive is irrelevant info and there's no harm in removing it.

Furthermore, there's this ELU question with a good answer adjacent to it. Quoting the answer:

Talk to can result in a dialogue, of course, but marks the initial intention of a serious monologue, like:

I'm going to talk to my boss today and ask for a raise.

-> I will go to his office, give a serious speech and hopefully it will result in a rational dialogue.

We're having a party tonight and my boss will be there, so I'm sure I'll talk with him a lot.

-> We will have a casual conversation, but nothing too serious I'd like to give a speech about

As you can see, and as the accepted answer has pointed out, seeing chat and seriousness go together is a bit of a rare occasion. This also further explains why chat with is more common.

TL;DR:

• These pair of words are observed in normal conversation: Talk to/with, chat to/with and speak to/with.

• Chat with is more common than chat to by a large margin. However, talk to and speak to are more common than their corresponding phrases, also by a considerable margin.

• This can be explained by three factors:

  1. The verb chat itself has a subtle indication of an interactive and two-sided conversation.
  2. Many authors prefer to use the pairs talk to and speak to because they don't see it necessary to indicate the existence of a dialog rather than a monologue.
  3. One sense of talk to does imply dialogue, but also implies its seriousness; while chat is typically not serious.

• Thus, to answer the main question, chat with is more common than chat to. You may prefer to use whichever preposition you want in this case, based on the meaning you want to imply. But I suggest (not obligate) you use the with version, since people with similar interests (in your context) are unlikely not to have a friendly and casual conversation.

_{Due to avoidance of the stimulus "OH THE HORROR!" sympathetic response from the reader, the author did not discuss any other inflections or prepositions in this answer of his.}