We did a qualitative analysis of the various policies that editors of English, Italian, and French Wikipedia follow when adding (or not adding) inline citations, we categorized them into macro-classes, and summarized in this docuemnt.
When adding the {citation needed} template, editors also have the option to specify a reason via a free-form text field. We extracted the text of this field from more than 200,000 citation needed tags added by English Wikipedia editors and converted it into a numerical feature using Fasttext [1], then clustered them. Each cluster contains groups of consistent reasons why editors requested a citation.