If you used an INI file to edit your strings and imported it later into the CSF Editor program, you wouldn't have any squares or other stupid symbols in your string.
yep
you just have to export - at best the original - CSF file once and save it as *.ini and then you can easily put in new entries with the right syntax (really easier then with str files).
then when you have made some new entries you just have to import this INI file into the CSF editor and save it as generals.csf in the Data\English directory. Voilą: no stupid "fatal string errors" and squares.