My first response, upon reading
> Asfridhr's speculation was to say, "no, on the inside!" because that is the
> most common method I learned for darning/patching frayed fabric.
I found a mention of an item patched on the inside-- one of the hoods from Viking Age Dublin.
E. Wincott Heckett. 2003. "Viking Age Headcoverings from Dublin" (Dublin: Royal Irish Academy")
pp. 44, 46:
"In wool cap DHC32 (Pl. VII, Fig. 52) a large patch has been sewn to the inside of the right-hand part. The sides of the patch have been turned under and it has been slip-stitched to the inside of the cap. If the patch had been put on to over a hole, placing it like this on the inside would leave the rough edges of the tear exposed to view on the outside, which is contrary to usual sewing practice. Placing the patch as it is means that the smooth surface would have been against the wearer's ear. This may suggest that the patch was put on to provide extra protection and warmth, or to strengthen a threadbare rather than a torn area. It may also be that it was unimportant that ragged edges were left on the outside. This would be true if the cap was worn under another headcovering or indeed as a nightcap."
There are other patches in there, too, but I thought this particular one on the inside might be interesting as a possible exception to the rule. :)