Blog Post
In our testing we are not able to find this as a difference because in 18.7 we still see that username is displayed in Quoted reply so what additional changes we are getting in this fix
"Previously, when users who were not permissioned to use the @mention feature clicked the “Quote” button when replying to a post, the name of the user being quoted did not appear in the quote/reply. We have fixed the issue and now the username appears in the the quoted reply."