It can be done with uBlock [0] writing custom filters though one would have to write a filter for each domain as the stylesheets differ.

Here is an example of how to do this on HN in about:addons -> uBlock Preferences -> uBlock My Filters tab

    # top (title / url)
    news.ycombinator.com##tr.athing span.titleline > a:has-text(/(musk|elon|twitter)/):upward(tr)
    # bottom (stats / comments)
    news.ycombinator.com##tr.athing span.titleline > a:has-text(/(musk|elon|twitter)/):upward(tr) + *

Or if you just want to replace text, there is the FoxReplace addon. [1] One could rename him to whatever brings a smile.

[0] - https://addons.mozilla.org/en-US/firefox/addon/ublock-origin...

[1] - https://addons.mozilla.org/en-US/firefox/addon/foxreplace/