Just like we can put unwanted circulars straight into the bin, walk past a footpath speech-maker, or ignore every comment on an online article, any private person or company is free to delete a comment on social media for any reason. It doesn't have to be offensive - if it's funnier than your original comment, or an awkward non-sequitur from a relative who has just learned to use "the Facebook", feel free to delete.
On most social media platforms, users are not able to delete comments in bulk. Twitter's Help Centre, for example, confirms that Twitter does not offer a bulk-delete function.
Individual deletion would be a laborious task indeed for those with millions of followers looking to get rid of hate, negativity and weight-loss spam.
However, the Internet is now chock-full of a rumour that certain celebrities have been given a special tool to bulk-delete comments on Instagram, based on the use of certain words or emoji.
So what? Well, in the mind of an internet troll, the right to freedom of expression is conflated with the non-existent Right To Be Listened To (as well as the mythical Right To Be Agreed With, and Right To Be Free From Ridicule).
But of course, the likes of Taylor Swift could afford to pay a room of Individual-Comment-Deleters, if they wanted to. A tool for bulk-deletion of unwanted comments is no different. Just more-efficient.
The right to say what you think is not a right to demand that the thought be read, let alone preserved on a private platform.