So its not a good idea to use the additional essay to showcase whatever lil community service I have done??
I echo kryzak's sentiments. If you find space anywhere else in your application where u can include community service go for it.
Else as an optional essay, you can write it, but I think that essay will sound too fluffy.
I mean can you write a 500-1000 word essay on your community service. Unless you work in social services or were a NGO, it would be hard to talk about it without putting in filler. you are saying you have lil community service.
You want to use that in ur package to show some diversity. The idea is good but it can backfire if you dont have enough material.
I would recommend not to use the essay unless the community service was very very important and significant.