you can find plenty of hints if you search for phrases approver comments and regular expression

https://community.nintex.com/search?q=Approver+Comments+regular+expression 

note to say that whatever complex regular expression you build it will not be reliable since you can not avoid that a pattern to be excluded by a regex doesn't appear within youor approver's comment/text

only reliable way to get approver comments is to get them from task list

https://community.nintex.com/message/30631?commentID=30631#comment-30631 

Hi Marian,

I admit that the best approach is to have it from Task list, can you please shed some light on the below query then.

My request review task is getting assigned to a group of users with any one user's review is mandatory. In that case how can i loop through the task list to find out the responded user. I know this much ie, 1) Store task id's in a collection variable on Create Flexi task action

2)Iterate the workflow task list with the task ids'

3) Query (How to identify the respondent & comments)

approver is stored in 'Assigned To' column

comment is stored in 'ApproverComments' column

Hi ‌, have you resolved this?

If so could close the topic and select a correct answer?