Having just made placemats for our church bazaar, you grabbed my attention. Note: in all the years I've quilted and sewn, I have never made placemats!! Simply put, I don't use them myself, so hadn't made them for anyone else. Well, that is, until the church ladies requested them!
I really did not know what to use for batting and just went with a poly/cotton that I had here already. Not too thick, but seems to show enough definition to the quilting. And with enough weight, that I felt there was some protection and that it had a nice texture/feel, without being too overly bulky.
Though I did wonder (and still do) ... what about a layer or two of flannelette?
I have LOTS of it in stock, and would really like to downsize that part of the stash!!!
(now that I am into making placemats!

)
So, am throwing flannelette as a batting into the discussion as to its appropriateness for placemats, along with yours,
@GingerK !!