Dunno about the others, {{sup|...}} behaves exactly as you describe, on en at least.
Really?!? I'm gonna hafta' dig deepa' wid this stuff :)
One possible benefit of such templates is that they become documented in a predictable place. Simply search for template:sup and you'll find what it does, and when to and not to use it. How would you find out what <sup> did?
Same way I learned just about every other tag/directive/class, etc. I read a book (or two or seven). I'm a great believer in reading then doing, though there is no experience quite like the one afforded by raw empiricalism (warts and all). There is no better teacher than making a mistake and no better student that the one that admits the error and learns from it. As Piet Hein said (and I paraphrase) "The secret to success is to err and err and err, but less and less and less."
But that's just me.
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