On the All Comments screen, you have a number of filters available to you that make it much easier to deal with the large volume of comments that you'll be receiving.
One of those filters is for Tags that you can add to Comments. Tags allow you to group Comments together in a way that makes sense to you.
Adding a tag is easy, simply click on the Add Tag button or little blue plus sign. This creates a block in which you can type a new tag. As you type, previous tags that you've used will be shown. Once done, hit enter or click the little green check sign. The new tag will be added immediately.
Now that you've added some tags, you can easily filter the comments by them. Simply enter the Tag you'd like to filter for in the Search Tags box and click Apply. You'll notice that tags that you've already created are once again presented to you as you type.
Tags are a great tool for organising comments in a way that makes sense to you. This will make it much easier to deal with the large volume of comments you'll collect as you send out more surveys.