I am using \buildtextaccent to create a couple of characters that have 
no Unicode equivalent. They are scribal abbreviations that made it into 
early typesetters works. In this case, the abbreviation are for Latin 
que, which looks like a q with a small ezh appended in a subscript 
position, and q with an acute accent, both of which are used in some 
17th century works I am dealing with. An example of the abbreviation 
with the ezh and accent can be seen at 
https://books.google.com/books?id=hHNVAAAAcAAJ&pg=PA6#v=onepage&q&f=false in 
the sixth line of the paragraph beginning “Yea but”.

It seems that \buildtextaccent\textacute q (or \buildtextaccent´q) moves 
the q to the right within the character’s bounding box. The following 
example (and attached resulting pdf) demonstrates this. Lines 1 and 2 
show the string with and without the \buildtextaccent, and lines 4 and 6 
repeat that in italic.  The strings are the same width, but the q is 
moved right. Lines 3 and 6 show a manual kerning of the q to improve 
appearance.

This happens with many fonts, but not all (I do not see it with Computer 
Modern). I am using Win 10Pro x64 with ConTeXt  ver: 2015.09.04 11:00 
MKIV beta  fmt: 2015.9.5  int: english/english.

I suspect that this is not intended, but I am not sure.

I would also love to raise the accent a bit. Suggestions? I can live 
with it as it is and manually kern as needed. There are very few 
instances of these abbreviations that need to be dealt with.

    % macros=mkvi engine=luajittex

    \starttexdefinition boxWidth #STR
       \setbox0=\hbox{#STR}\the\wd0
    \stoptexdefinition

    \starttexdefinition Dicitque
       Dicitq\kern-0.070em\low{ʒ}\autoinsertnextspace
    \stoptexdefinition
    \starttexdefinition DicitqueK
       Dicit\buildtextaccent\textacute
    q\kern-0.070em\low{ʒ}\autoinsertnextspace
    \stoptexdefinition
    \starttexdefinition DicitqueKK
       Dicit\kern-0.060em\buildtextaccent\textacute
    q\kern-0.070em\low{ʒ}\autoinsertnextspace
    \stoptexdefinition

    \starttexdefinition idque
       idq\autoinsertnextspace
    \stoptexdefinition
    \starttexdefinition idqueK
       id\buildtextaccent\textacute q\autoinsertnextspace
    \stoptexdefinition
    \starttexdefinition idqueKK
       id\kern-0.060em\buildtextaccent\textacute q\autoinsertnextspace
    \stoptexdefinition

    \setupbodyfont[ebgaramond,12pt]

    \starttext
    \startitemize[n,joinedup,packed]
    \item \Dicitque \qquad\boxWidth{\Dicitque}\par
    \item \DicitqueK \qquad\boxWidth{\DicitqueK}\par
    \item \DicitqueKK \qquad\boxWidth{\DicitqueKK}\par
    \it
    \item \Dicitque \qquad\boxWidth{\Dicitque}\par
    \item \DicitqueK \qquad\boxWidth{\DicitqueK}\par
    \item \DicitqueKK \qquad\boxWidth{\DicitqueKK}\par
    \stopitemize
    \startitemize[n,joinedup,packed]
    \item \idque \qquad\boxWidth{\idque}\par
    \item \idqueK \qquad\boxWidth{\idqueK}\par
    \item \idqueKK \qquad\boxWidth{\idqueKK}\par
    \it
    \item \idque \qquad\boxWidth{\idque}\par
    \item \idqueK \qquad\boxWidth{\idqueK}\par
    \item \idqueKK \qquad\boxWidth{\idqueKK}\par
    \stopitemize
    \stoptext

-- 
Rik