> Alan Bowen <mailto:bowenalan03@gmail.com>
> 19. Oktober 2016 um 17:15
> \starttext
> \startblockquote
> [w]hile we may
>
> [w]hile we may
>
> \stopblockquote
> \stoptext
>
> seems to fail with the latest beta (ConTeXt  ver: 2016.10.14) unless 
> one replaces the first line with
> \[w\]hile we may.
>
Better \startblockquote\relax

The \startblockquote command has a optional argument which is passed to 
\startnarrower and
in your example [w] is used as the argument. This alone won’t be enough 
for an error, the reason
why you get problems is that \startnarrower takes everything which isn’t 
a valid keyword (left, right
or middle) as dimension for the margins but "w" isn’t a dimension and 
generates the error.

Wolfgang