I have no idea what the sequences like "\v!"and "\c!" etc. mean. Are they references to modes?
I asked much the same question on tex.stackexchange.com two months ago, except mine was not so nice and focused. Aditya gave a very nice explanation of what the letters do; clearer than the one on the wiki, I thought. Here's a link straight to his answer: http://tex.stackexchange.com/a/58716/2229 They are used as language-agnostic forms. Using ConTeXt's English format, you'd type \startmarginblock Using ConTeXt's French format, you'd type \demarreblocmarge So to accomodate both, we define variables \s!start --> start or demarre, and \e!marginblock --> marginblock or blocmarge, depending on the language, and then we tell TeX we want to run the command named with the string \s!start\e!marginblock --> startmarginblock or demarreblocmarge. (Example not entirely accurate, I believe the variable for startmarginblock is define holisticaly. But you get my point.) Example of the need for the letter codes, paraphrased from mult-ini.mkiv: Where English uses 'left', in Dutch one finds both 'links' for '(on) the left' and 'linker' for 'the left one'. Hence the letter codes, so we can have \v!left --> links and \c!left --> linker. \c! is for keywords \v! is for value names \s! is for system bits \e! is for elements Hope this helps you in reading the sources! Cheers, Sietse