New SharePoint Online emails to keep you informed about likes and comments on pages/news posts are coming very soon.
After this change takes place, when someone comments on a page or a news post, the author of the post will receive an email. If this comment is a reply to a top-level comment, the top-level commenter will also receive an email. Comment emails will be batched so that your users will receive a single email when several comments have been made on the page or news post within a short duration of time. Additionally, the same functionality will apply when users leave a like on a page or news post.
Update will begin rolling out in early June, and completed worldwide by the end of June 2019.