Please follow the steps below to clear the comments in a worksheet:
Step 1: Select the whole worksheet by clicking the top left corner;
Step 2: Click the "Home" tab from the ribbon;
Step 3: Click "Clear" in "Editing" section and click "Clear Comments and Notes";
Alternatively, select the whole worksheet, right click and select "Delete Comment" from the list.
Step 4: This is to remove all the comments.