I asked my teachers and mentors for LORs and later when I asked them how it was going, almost all of them said that they have mentioned a few of my extracurriculars in their LOR (which I have already listed in the Activities Tab or the Additional Info section of the Common App).
Is it okay for my recommenders to mention my ECs which I have already listed on the common app?
When your teachers and mentors mention your extracurriculars, it shows that they have gotten to know you as a person rather than just a student in their one subject. It can't really hurt you to have your ECs mentioned more than once, and you don't have control over exactly what your recommenders write about you, so it isn't worth having all of your letters be rewritten.
Best of luck in applying!
Yes, this is definitely fine. As @sebills mentioned, the fact that your teachers know you well enough that they feel comfortable to talk about your ECs just points to the type of student you are and your relationship with your teachers. You're not just another student in their grade book, you're someone they've gotten to know on a personal level. Plus, as @sebills also mentioned, you don't really have much control over what they say about you in those letters so a college isn't going to look down on the fact that your teachers mentioned something that can be found in other parts of your app.
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