Are you trying to include the additional comments all in the same line, or do you want them as separate entries?
If you want them on the same line, just retrieve the field value, then include that token in front when you update the field.
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However, if you want it to have multiple "comment" entries, which seems more appropriate for what you are trying to accomplish, you need to go into the Admin Console, change your comment/remarks field to "Allow multiple values"

Then in your workflow you will have three options (in a column to the right of the "value")
- Append to existing values
- Replace existing values
- Clear all values
In your case, you would want the first option, and with that configuration every time you update the field it will add another box with the new value under the same field label: mutiple values, but they will still be kept nice and separate.