The thanks is a great idea, especially for a learner as they are just gathering up facts and it is a lot to swallow first up and it's just an acknowledgement that the reciever is thankfull for your reply but hasn't yet got much to reply about other than thanks.
I have seen so many times were some people have put in a lot in their answers but the poster doesn't even acknowledge them and will skip a few posters and only answer one or sometimes knowbody, now that is straight out rudeness in my book, a simple " thanks to all " at the end is really appreciated.