As they explained from arrowchat support, this is because the chat makes post/get requests, which makes xenforo show the loading animation every 1-2 seconds (the moving bars in the upper right corner). Are there other people using arrowchat with Xenforo? Am I the only one with this problem or do you have it too? How did you fix it?
From arrowchat support they advised me to contact xenforo support and ask them for a way to just hide the moving bars. I did that but of course xenforo support told me this is a problem with arrowchat and not xenforo and they can do nothing. And I should say I agree with them. I went on cometchat demo page, there was a demo of cometchat installation on xenforo where their chat worked on xenforo without causing this reloading. I believe - without modification of xenforo. So, any suggestions ... ?