Yes, hinder. It would basically make people use the forum less like a forum, because people would just hang out in the chat, then too many topics would be talked about, because it would be more convenient to post their query on there than it would, to create a topic, etc.
It's also similar to why the portal page has been discussed about if we should get rid of it or not. The portal page, while convenient to keep track of certain topics, only focuses on the topic that gets a lot of posts, thus bumping other topics to the bottom of the list, once a topic is off of the portal list, it's usually ignored, because a lot of us (myself included) usually never go beyond the portal section, so topics that aren't on the portal page become ignored.
Without the portal, users would be encouraged to look through the forum, now it may seem more inconvenient to do that, but that's why we have a search option.
Another reason why chat room isn't functional, is because we also like to save/archive topics, whether they are new or locked/old because other potential users (new and old) can still refer to those topics for future reference, or if they are new, any information would still be there for them to read. A chat wouldn't be able to be archived, so if someone talks about something with relevant info, it eventually gets lost and can never be traced back.
Now with a chat, I see it going one of either two ways.
1, it becomes so congested with so many active users, that everyone eventually stops using the forum and just chats in the chat room.
2, it gets completely ignored like last time.
Also, I think our forum software is limited to what it can do because it's a free service.
I believe we are still looking for a good forum service that we can transfer to, hopefully to one that can keep all our data intact (at a decent price that won't cost a tail and a fin). A haha see what I did there?