I should be working, but it’s a slow Monday morning so just for the fun of it, I found the sites you quoted. As outlined at the end, I come to a different conclusion. Of the sites, really only the first is authoritative, and it counters the misperception that there are any nonlinguistic differences between the terms.
The 1st source is from an online encyclopedia http://en.wikipedia.org/wiki/Seppuku and does a pretty good job of explaining seppuku. If you reread the article, it actually counters your argument.
This is what Javan, et al have been trying to point out, that while there is a difference in terms, and it’s analogous to the difference between a formal term and slang. The difference between “committing suicide” and “doing yourself in.”
This rather detailed article goes on to explain the different circumstances in which suppuku occurred.
It makes sense that there would be more ritual involved when committed as a protest, (if nothing else, thre is more time to plan) but, as you can see from this quote, it is still seppuku, even when done on the battlefield. This directly answers a comment you made earlier:
2nd quote
http://www.shmeng.com/modules.php?op=modload&name=News&file=article&sid=352
This is just a post on another board in response to an article “Philosophy on Suicide”. So another poster has the same misconception, this cannot be considered authoritative. (And I disagree with the article on what the author calls “the Japanese warrior perspective” which is an oversimplification.)
The 4th quote is the immediate paragraph following the 3rd quote, from
http://www.artelino.com/articles/samurai.asp
a website for art auctions. And again, although they don’t get it quite right, this quote actually supports our arguments that the terms are the same.
5th
http://celesstar.osiriscomm.com/anime/otaku.html
Titled Just What Is An “Otaku” Anyway? A Guide To Useful Japanese Terms Found In Anime.
The author mangles other Japanese terms as well, for example: “Kohai - An underclassmen” showing a lack of understand the language.
Of the five quotes from the four sources, the only two which support your argument are the post on another board, which is propagating the same misunderstanding, and then an anime fan who doesn’t have a good grasp of Japanese. I’m not really sure I would want to base my arguments on sources such as this. The best source which you quoted, the encyclopedia, actually refutes your argument.