As a follow up to T419466: Spike - Title normalization is not applied when saving pages to the reading list via the API and T422028: Normalize ReadingLists entry page titles on database reads and writes, when the ReadingLists API endpoints query and fetch reading list entries, we should ensure the page titles are formatted with spaces:
strtr( $row->rle_title, '_', ' ' )
This ensures consistent formatting of the page titles regardless of how they are stored in the database.
When we implement this, there should be tests that cover this behavior.
Formatting the titles with spaces will be compatible with the mobile apps, without required changes to the mobile apps.