All characters that are set as starter strings for sections are recognized by Doc-O-Matic. If a starter string is not recognized section delimiters might be missing. 

Assume starter strings of a section of the ignored text type are set to the characters #X#. The following comments:

result in the documentation text: 

This is topic1.#X# This text should not be shown. 

You can run into problems, if you do not use section delimiters, but place section text and section starter string on the same line. To use spaces as section delimiter, turn on the option Allow spaces as section delimiter on the General Settings > Sections > Section Delimiter page. You can use both methods:

Both comments result in the documentation: 

This is topic1.