Find if value already exists in list and do not return duplicates

HIi KMK82 ,

By default, in SharePoint Online, notifications are only sent when an @ mention is used in a comment. There is no built-in way to receive notifications for comments that don't contain an @ mention.

However, you can create a custom solution to receive notifications for all comments in a SharePoint list. One way to do this is to use Microsoft Flow or Power Automate to trigger an email or a notification when a new comment is added to the list. You can set up a flow that triggers on the "When a new item is added" event, checks if the comment field is not empty, and sends an email or a notification to the desired recipients.

Note: This is an advanced solution that requires knowledge of Microsoft Flow or Power Automate. If you're not familiar with these tools, you may want to consider seeking help from a professional developer.