Much of the content of Dennis Polis's post I would concur with. The target paper seems to be based on an externalist view of concepts of the sort that Hinzen, in my view successfully, sets out to demolish in his Essay on Names and Truth (Oxford 2007). I would agree with Polis that concepts are primarily defined in internal terms - either as components of experience (if often 'thin') or as the internal resources that generate those components of experience. The resources that generate associated sensorimotor events are only contingently associated. 

I have sympathy with a desire to banish 'concept' from a research environment if the word has become imbued with adverse theoretical presuppositions - particularly externalist ones. But that does not seem to be Stevan Harnad's motivation. What I find interesting is that both Polis and Harnad seem most at pains to avoid implicating 'homunculi'.

I continue to be puzzled by the claim that an infinite regress occurs when postulating homunculi, at least defined as subdomains of the brain that receive, from other parts of the brain (such as V1 etc), the inputs that form the basis of the experience of what Polis calls 'I'. It is widely acknowledged that such a regress only relates to Dennet's 'straw homunculus' that repeats entirely the talents it is rung in to explain: probably only postulated by anti-homunculists. If it is possible to explain the association of experience with the biophysics of a whole human body, nervous system or brain, whichever preferred, then it is presumably possible to do so for a subdomain of brain. Moreover, neurobiology suggests that the contents of experience are encoded in restricted pathways that carry data selected from a wide range of sensory and subliminal memory data, not to mention skeins of housekeeping interneuronal pathways.

My impression is that the real impasse in philosophy of mind is a fear of accepting that percepts and concepts, including the sense of being 'I' are part of the experience of inputs to very small components of brains. Homunculi are absolutely fine; there is no need to be frightened of them. They are very likely us and have concepts encoded in their inputs. I would submit that if we try and find out what they might be then we might explain what concepts are.