Hello @splaquet,
Thank you for your interest in our Database Collation Fix tool.
The reason this tool was created was to change a database’s collation algorithm AWAY from utf8mb4_unicode_520_ci. This is because at the time, the utf8mb4_unicode_520_ci algorithm required MySQL v5.6 or later and many hosts did not yet support that. Also, many hosts were using MariaDB instead of MySQL and MariaDB also did not support the utf8mb4_unicode_520_ci algorithm.
This meant that if you exported your utf8mb4_unicode_520_ci collated database and tried to import it into these non compatible version, the import would fail. You would then need to tediously edit the .sql file and change the collation algorithm references.
So we created this tool to help move you away from the less compatible utf8mb4_unicode_520_ci collation to utf8mb4_unicode_ci, for example. And if you set the collation in wp-config to use the 520 algorithm, we specifically ignore this in favor of the more compatible algorithm. This was done on purpose, not as an oversight.
All of the utf8mb4 collation algorithms support Emoji characters. So even when using utf8mb4_unicode_ci, you’re fine.
If you would like to enable the use of the utf8mb4_unicode_520_ci algorithm, you could always modify the code and remove that from the $_change_collation list, allowing the wp-config setting to be used.
All the best,
The ServerPress Team
