Prior to FontAwesome 6, the usage of icon was done like this: <i class="fa fa-save"></i> Starting FontAwesome 6, the classname fa is converted to fa-solid or fa-regular in order to choose a style for the icon.

While the recommendation is to use FontAwesome 6, there are still parts of the code that use legacy fa fa-save. And since developers copy paste snippets of code for new contributions, in the code review we are sometimes rejected because we didn't see that we need to convert to fa-solid fa-save.