So basically we know these things:
1) On I-85, the signage reads "To"
2) But, upon exiting I-85, there are shields without "To"
3) Then there is one solitary standalone US176 sign southbound
4) The SC Log file says the highway ends .18 miles north of BL85
5) But, signs continue (northbound) for about .64 miles past that point
6) The distance between the signs at Item 2 and Item 5 is about .36 miles
7) The distance of Actually Signed vs. Official (Item 5) is greater than the distance "Unsigned" (Item 6).
8 ) There is also MM1 one mile south of the I-85 interchange, meaning it's being marked from I-85
To me, that says just label the whole thing. I think if Item 3 didn't exist, we wouldn't even be asking the question. One "forgotten" I-585 sign doesn't negate the other info for me.
Chris