I've seen pegged tenons pulled apart in buildings that are mere infants compared to the English frames, like only 100 years old or even less, on the topic of infant lap joints pulling.
The success depends on execution every bit as much and more than it does on theory. I could make a mechanically perfect joint but If I make it with a bad piece of wood or build the structure with a poor understanding of loading and structural forces and therefore give the joint stresses in multitude and direction that it simply wasn't designed for (or do the same by setting it on a poor foundation) then the joint will fail, sooner or later.
On the other hand, I could make a 'lousy' joint that in a well executed frame might last 1000 years or so. Or I could make a good frame and not bother to peg anything, and have absolutely no problems as a result. There are some old building traditions in Europe that don't rely on pegs very much at all, and incorporate many joints besides mortise and tenon. For example, look at the way the Germans handle the problem of tie beams. Google "Einfacher Kamm" or "Gerader Kamm" -they totally do away with the mortise and tenon for this altogether, and instead sandwich the timbers between two plates, which also allows them to get away with using fairly small timbers. (I know I reference the Germans and the Swiss a lot, but that's because it is something I am familiar with.)
In my study of the Swiss buildings, I find that nearly all of the very oldest buildings in the particular style that I have been studying employ lap joints for the braces, sometimes half dovetail laps, sometimes just plain half laps. It could, however, attribute some of its success to the fact that the builders of these buildings seemed to have braced them excessively, or at least to a higher degree than we might think is normal. However, it seems that in many cases these joints are designed to resist tension as well as compression, even though they are primarily in compression (wind loading causes that to happen at times to wall and roof braces)
Now back to the original question,
I would caution against single sided pegging, as that could potentially put a lot of stress on that one side of the mortise which could cause joint failure (COULD, not WILL) Even if you intend pegs as an assembly aid and not vital to the strength of the assembled joint (which in my opinion is how joints should be designed, although that is my opinion and I realize there are many others out there who feel differently than I do) the peg WILL at least on occasion put pressure on the mortise side. SO I would recommend going all the way, or at least most of the way, with your peg.
Brad has some good advice there, try not to read insults into things. And try not to make them inadvertently. I try my best to always assume that someone isn't trying to insult me, even if it's very hard to do that. I find that life becomes more enjoyable if you aren't offended all the time (which being offended is usually your choice)
