It wasn't an overprint -- it was part of the map. Look at the lower left corner of the map where there is a very cursory legend that explains a few symbols including this one. It is a marked boundary between Alasa Farms land and DEC land. It's crossable as stated in the mini-legend. There are blaze marks on trees that are reasonably visible and thus makes sense to have on the map. Plus it lets people know that this is NOT an uncrossable boundary that they've run into.
The maps I saw that were blown up from the 1:10000 scale were lacking the legend - I don't know if brown was in the category or not. And I'm not sure how many people who had maps with the legend realized there was one - I didn't see it until after the fact.
The non-standard boundary symbol confused a lot of people, especially because it looked like the ruined stone wall symbol (but larger and in the wrong color). What is used on other maps? Rotary Sunshine seems like another map that would have a similar issue, as the boundary between the camp and Rush Oak Openings is crossable. It seems to me an option would be to use the IOF (uncrossable) boundary symbol and make it clear that it is crossable by having the course go across it and out-of-bounds marking on the outside of the uncrossable boundaries, or another (perhaps better) option would be to use a dashed purple line for crossable boundaries (not standard, but closer). It was also a bit baffling to have the boundary line have large gaps - I assumed it was to avoid obscuring features on the map, but that contributed to the idea that is was some intermittent fence or wall.
It would probably also be a good idea to call attention to non-standard map symbols and procedures (such as a remote start triangle) in the meet notes and on the listing of courses - people may still miss the information, but there's a better chance of it being seen.
Doug is the one who noticed and mapped the boundary line. My assumption is that the gap was in fact a gap in the blazes -- that they were present and visible in the areas where the lines were, but either totally absent or possibly extremely subtle in where there was the gap in the line.
Rotary does indeed have an identical situation -- boundaries which are crossable. That map used a greenish colored solid line with tags on both sides of the line to indicate that neither side was out of bounds. I suspect there isn't any real standardization for that type of boundary. I know there are some CNYO rogaine maps that have that situation but I can't recall what they used.
I agree with all of Stinia's points and observations by the way.
CNYO uses a red dashed line for all boundaries with tags on the state land side(s). They have also sometimes used gray contours or gray shading or even red/purple overprint on the (OOB) private land. You can also tell most crossable boundaries because there are controls on both sides.
For regular O maps, though, I think it is best to stick as close to the IOF standard as possible - so solid purple lines for uncrossable boundaries and [something] for crossable ones (no IOF symbol for that as far as I could find in a quick search of the mapping specifications). It would be good to be consistent within our own maps even if there isn't a more widely accepted standard.
Uncrossable boundaries are shown on the map whether or not they are visible in reality, so I think that the state land boundary should be shown where it lies and not only in places where there are visible blazes or signs. (That would also make it clearer that it isn't some feature like a wall.) Meet notes could indicate if it is reliably marked or not, though how important that is to do would depend on what the typical assumption is - do people expect boundaries to be visible in the woods or is there a general understanding that they may or may not be marked?
I think it is useful to show the state boundary on the Alasa Farms map since it is marked in at least a few places (I saw a state sign and a yellow blaze at one point, and a No Hunting sign when I came back) but it is perhaps less important to do so if there aren't any POSTED or No Trespassing signs - those are the things that give an "uncrossable" impression. I think Rotary Sunshine does have some version of POSTED signs so there it is more important to convey that those can be crossed.