In Drupal 8, classes that are used in order to implement a content entity (which extend the ContentEntityBase class) have a validate() method that validates the values entered when creating the entity.
A similar method should be introduced in Backdrop and added to EntityInterface.
GitHub Issue #:
6061
Recent comments
There is also Node Comments Search - this searches the node and all comments (default search is node and first page of comments) as part of the content search. Izzy's module above is a separate...
Search does not include comments
I have created a new module comment_search
Search does not include comments
If there is no response, alternatively, you can use a View with a list of comments, with a filter based on the comment text. I haven't tried it myself, I just got an idea.
Search does not include comments