Why does the sort order (for registers, lists of synonyms, and so on) differ when no method is specified compared to when method=default is specified? That is, should not the default method applied when no method is specified be that named ‘default’?

\setupregister[index][n=1]
\starttext
\index{Abc, def}\index{Abcdef, ghi}\index{abc, def}\index{abcdef, ghi}

\subject{Placeindex with no explicit method}
\placeindex

\subject{Placeindex with \quote{default} method}
\placeindex[method=default]

\stoptext

Where can documentation of the four defined methods (apparently: first, last, before, after, and default) be found? Where can documentation on the use of method mapping and cases, and unicode ordering, be found, or at least something not as cryptic as found on the mailing list[1]?

[1] http://www.mail-archive.com/ntg-context%40ntg.nl/msg50454.html
--
Rik