ignore specific lines and portions of lines
Ignoring lines or portions of lines is best described using file specific information. This is why ECMerge has "File types". It allows you to confront files of slightly different types in the same comparison.
For example, imagine you have log files (named *.log) where comment lines are noted using # in first position and every other line is started by current date finished by some ": " (colon space) notation, you would do that way:
Now open the log files to compare, unimportant portions of the file are ignored.
Note: you can Export and Import later a file type on the same or another computer