This still doesn’t explain why overlapping rooflines are actually problematic, though. I have always wondered this myself, as I actually own a house with a detached garage where the previous owner and next door neighbor put an easement on file that allowed the next door neighbor (whose ground level is about 5 feet higher via a retaining wall) to build an outbuilding very close to the property line with the roofline hanging over my garage by about 6 inches. So far, the only practical downside is that my downspout ends up getting all the water from half of his roof, which means the problem is worse if I don’t keep it clear. Not a terribly big problem in my book, since I have to keep it clear anyway. What else am I missing?

(Note: there are other things that are suboptimal about my garage, namely that it was built 100 years ago right on the property line and when it was rebuilt sometime later, it was allowed to stay there despite normally having a 5 foot setback requirement. As a result, this concrete block structure itself actually serves as part of the retaining wall and has moisture seepage issues from the uphill side. I actually think having the neighbor’s outbuilding covering that patch of land and managing the rainwater via my downspout helps the matter, because the ground between them gets no rainfall at all.)

This is exactly the reason I asked for reasoning. A perfect example of a specific reason for something in code where depending on what you are doing yourself you can safely ignore the code violation (except for the legality part). If the reason you gave is indeed the reason and only reason.

I would argue that if inspections for safety reasons are why this is in code then code needs to remove this restriction and other rules should be put in place and inspections should become less expensive, easier to get done etc. Basically make it easier and less of a problem for people to get inspected. You will still get people that won't do one of course. Make it possible to inspect them anyway. Of course I understand that there are conflicting priorities at work here too. Meaning funding. The optimal way for everyone would be quite expensive. So we get suboptimal solutions that are sometimes "OK" to circumvent and sometimes not.

Here the bylaws for example allow one main structure, a shed and a detached garage (even if you have an attached one already). No need for roof overhang code stuff. The intent of the bylaw is also much more clear.

The guy in the article arguably is creating such a detached building. He is also in violation of rules about how far structures have to be from the property line assuming the rules in his place are like here and that fence is towards the neighbors.