The computer at every walmart I've ever been to (a lot) says the ST6607 is the correct filter and their book says so too. I have noticed that it recommends the 7317 in the non supertech brands so I have used that size when they didn't have the st6607 on the shelf. Googling 6607 and civic shows threads where other people have used it. I imagine thousands/millions of the st6607 filters have been installed on civics at this point. If this were an issue I think there would have been a lawsuit by now. I probably won't buy the 6607 size again because the ST never seems to be in stock and the MP is a bit expensive for a supertech filter. I think I'll just order some filters from rockauto from now on.
It's kind of odd that they spec the 6607 when there is a supertech 7317 also. I have seen the smaller filters cause VTEC issues occasionally (on the 2.4 engines) but 99.9% of the time the shorter filter is fine