1) Schwartz's friend and MLJ co-worker Joe Edwards said in an interview with Jim Amash in Alter Ego magazine that Schwartz added the extra "M" to the end of his first name -- he had previously been known just as "Sam" -- for no reason, "just to be different." Shades of Ted(d) Pierce.
2) After writing it, I found another article about the launch of the "new" Jughead series in 1987. It doesn't mention Schwartz, but it says that the new series and the new approach -- trying to give him a love triangle a la Archie -- was a response to the "flagging sales" of the title and the perception that girls didn't want to read about the adventures of a woman hater. That suggests that the removal of Schwartz was part of the attempt to give the title a more girl-friendly feel. The love-triangle thing didn't last, of course, because nobody wants to see Jughead that way (as the company had already learned in 1978-9 -- but that's a story for another time). The reason I liked Jughead stories the best as a kid are probably the very reasons why they were the least favorite of the comic's broad readership: they are basically pure amoral comedy, almost like old-school studio cartoons (the best Archie stories are a lot like classic cartoons: variations on a theme), and while Jughead is a generally good guy when it counts, he's a terrible role model for kids. (This was actually the subject of a Schwartz-drawn story where two kids start to admire Jughead because he proves that you can eat anything you want and not get fat). The love-triangle experiment failed, but Jughead continued to succumb to the epidemic of Nice that had turned all the main characters into shadows of their '50s and '60s selves.
Update: Here's a scan of the news article I mentioned (click to enlarge):
3) Sam(m) Schwarts not only drew himself into the strip frequently, in the form of posters telling us to "vote for Sam" (or "Samm" depending on which spelling he felt like using), but when he moved to Miami, he drew a story -- I'm not sure if he wrote it or if Doyle did it -- called "Sam has moved to Miami," where Jughead is distraught because his unseen friend Sam has left town and moved to, well, I've already said it twice. The underlying joke of the story is that the never-seen Sam clearly wants to get the heck away from the freeloading Jughead. But it's got to be one of the few stories in this comic's history that's (sort of) about one of the cartoonists, and I fully expect the name "Sam" to be replaced by some other name if they ever reprint it in a digest. Note the Schwartz trademark of Jughead's feet straggling into the panels below him.
4) My earlier post about Schwartz's "El Slobador" story has been revised to include some screencaps. Turns out it was from 1974 rather than later, as I originally thought. It has to be one of the few issues of Jughead that's all one story instead of three or four separate ones.