French spacing

In English, the space after some punctuation (most notably after period) is wider than a usual one; this is a standard behaviour of ConTeXt when typesetting in English. If you want to disable it, in plain TeX or LaTeX you would call \frenchspacing. In ConTeXt, you may say

\setuplanguage[en][spacing=packed]

instead.

Here is a nice tweak:

\enabledirectives[characters.spaceafteruppercase=normal]

\vbox{\hsize 5em x. X\par x.\ X\par X. X\par X.\ X\par}

By default space after uppercase followed by punctuation is set to traditional which enables a somewhat special hard coded hack in the tex engine where characters with sfcodes 999 nil a following spacecode setting, even when it's triggered by a \ .