The option to comment on questions is very useful for developing and testing the questionnaire. However, it is not at all appropriate for respondents to give substantive answers to survey questions (of the text type, i.e. 'open-ended questions (see Q5)') simply in the form of comments, as comments are not stored in the database on which the analyses are later based, but only in the comments database.
You can access the comments settings in the 'EDIT' – 'Settings' – 'Comments' tab or by clicking on the chat bubble icon in the top right. Once commenting is enabled, you can access the comments in the 'TEST' - 'Comments' tab by clicking on the aforementioned icon, or in the 'EDIT - Questionnaire' tab, where the comments are available under the individual questions.
Commenting (or testing) is so important for the development of a survey questionnaire that we recommend using it for practically every survey. It is particularly useful and effective when using comments to replace the development of a questionnaire in a word processor (e.g. MS Word) and the exchange of versions via email.