Hi Patrice - If you write to the tex-live list, more than likely I will end up being the one who answers, so we might as well continue here :).
What is the question? I don't understand how or why we got on to LaTeX. LaTeX cannot possibly enable microtype by default, if that's what you were speculating about. It would destroy compatibility, since every existing document would be typeset differently. Among other things. (And for the same reason, I'm still not sure it's a good idea to enable it in Texinfo by default either, but since Texinfo usage is relatively limited, maybe it's ok.) As for cm-super, there is only one cm-super package / set of fonts. texinfo.tex uses cm-super just for a few characters (eth, thorn, ogoneks, and so on) that don't exist in the cm fonts. Actually texinfo.tex (and LaTeX) use the EC .tfm files for the needed fonts; cm-super provides the Type 1 fonts on the backend for those metrics. BTW, neither microtype nor cm-super are part of core LaTeX, in the sense that they are maintained by other people, and LaTeX can be successfully used without them. Microtype is entirely optional, and cm-super is not always needed, depending on encodings and font formats that are used. --best, karl.