Use the LISP application by CAD Studio (ARKANCE) - srxText (see Download) to add digit-triplets separators to existing drawing texts/figures. Use the Regular expression option of the text replacement command.
The search/replace expression for thousands separator (",") can be e.g.:
-?\([0-9]+\)\([0-9][0-9][0-9]\)
\1,\2
You may need to repeat this for millions etc. (srxText can be scripted). It will change:
1234 -> 1,234
-1234.5 -> -1,234.5
Update: the newer version of the command - SRXTEXT2 - has easier, VBscript-like formatting of the control codes.
For this thousands separator task, you can use the following, more flexible search/replace code:
(\d)(?=(\d{3})+\b)
$1,
Load the VLX file with APPLOAD and type SRXTEXT. See Readme for other examples of complex text replacements.