Those are brackets instead of parentheses because it’s not side commentary, it’s editing of a quote. https://writingcommons.org/open-text/research-methods-methodologies/integrate-evidence/incorporate-evidence/453-inserting-or-altering-words-in-a-direct-quotation
This does not make a compelling argument. I’m not saying bots don’t matter, but that study, in particular, is pretty meaningless. Counting the percentage of links shared tells you nothing about what tweets people are actually viewing and engaging with. What’s more, if a friendly bot gives you a useful link, is that bad?