Using both TL2013 and the current standalone beta (2014-03-16) I see a 
spurious comma in index entries referring to endnote locations. The 
following MWE shows the problem:

    \setupnote[footnote][location=none]
    \starttext
    Index in endnote.\footnote{\index{Why a comma?}Endnote.}
    \placefootnotes
    \placeindex
    \stoptext

-- 
Rik