EscapeE ignores any PCL commands which would have no tangible effect, such as switching between draft and letter-quality mode.
EscapeE also ignores PCL commands which it does not recognize. There is a huge range of printers supporting different levels of PCL, and some of these make use of obsolete or undocumented PCL commands. There are also a number of obscure or rarely-used commands that have not been implemented in EscapeE. These unknown commands will be ignored, which will not usually cause a problem, but if the appearance is incorrect see Problem reporting for details of how to send RedTitan the file for analysis.