Hi @jaWa ,
Nice to meet you again.
Comments follow the permission settings inherent in SharePoint Online and Microsoft Lists.
- Users with read-only permission can only view comments.
- Those with list edit permission can make comments as well as delete comments
- Editing comments is currently not possible.
According to my research, SharePoint Online does not currently support editing comments, it is by design. You can refer to the following workaround:
- Delete the original comment and create a new comment

- Click Reply under the comment and fill in the information you want to modify.


For more information, please see the "SharePoint Online: All you need to know about Commenting in Lists" Blog.
Thanks,
Echo Du
==============================
Updated Answer ==============================
Hi @jaWa ,
We can use REST API to retrieve comments, and manage comments.
To get all comments from a modern page, make a Get request to:
#A page which has the id "xxx"
#/_api/web/lists/GetByTitle('Site Pages')/GetItemById("xxx")/Comments
#For example:
/_api/web/lists/GetByTitle('Site Pages')/GetItemById(22)/Comments


To get a specific comment from a modern page, make a Get request to:
#Where yyy is the id of the comment.
/_api/web/lists/GetByTitle('Site Pages')/GetItemById("xxx")/Comments("yyy")
#For example:
/_api/web/lists/GetByTitle('Site Pages')/GetItemById(22)/Comments(1)
Since each comment or reply gets a unique id, the method is same for deleting both.
To delete a specific comment from a modern page, make a Delete request to:
#Where yyy is the id of the comment.
/_api/web/lists/GetByTitle('Site Pages')/GetItemById("xxx")/Comments("yyy")
#For example:
/_api/web/lists/GetByTitle('Site Pages')/GetItemById(22)/Comments(1)
1.Use Chrome browser and install the "SP REST Client" extension

2.Pin the "SP REST Client" extension

3.Go to the Site Pages library page and switch to classic mode.

4.Then click the "SP REST Client" extension.

5.On the SharePoint REST Client page, entry the below REST API to the Url field:
#Where yyy is the id of the comment.
/_api/web/lists/GetByTitle('Site Pages')/GetItemById("xxx")/Comments("yyy")
6.Click SEND button

7.Go to the corresponding modern page and you will find that the comment has been deleted.

For more information, please see "Working with the Page Comments REST API in SharePoint Communication sites" article.
Thanks,
Echo Du
==============================================
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.