If I create a file with the text

Bold italic plain bold italic plain
bold plain bold plain
italic plain italic plain
 bold plain (leading space)

where each word has the appropriate attribute (bold/ital/none) set, and
write to an rtf file, then the first three lines have no 
space appearing after the first word.  The third line is formatted correctly.

The relevant fragment of rtf generated is (sorry about the long lines and
messy wrap)

\pard\plain 
\ltrpar\s1\cf0{\*\hyphen2\hyphlead2\hyphtrail2\hyphmax0}\aspalpha\ql\rtlch
\af3\afs24\lang255\ltrch\dbch\af2\afs24\langfe255\loch\f0\
fs24\lang2057{\loch\f0\fs24\lang2057\i0\b{\b Bold}}{\loch\f0\fs24\lang2057
{\i italic} plain {\b bold} {\i italic} plain}
\par {\loch\f0\fs24\lang2057\i0\b{\b bold}}{\loch\f0\fs24\lang2057 plain
{\b bold} plain}
\par {\loch\f0\fs24\lang2057\i\b0{\i italic}}{\loch\f0\fs24\lang2057 plain
{\i italic} plain}
\par {\loch\f0\fs24\lang2057\i0\b0  {\b bold} plain (leading space)}
\par 

which shows that the required space is missing after the first word of the
first three lines: a space following an rtf command is 
part of the command, and not for output.