I’m making a blog/portfolio which I would like to look somewhat professional and I was wondering if me removing the theme author’s and hugo attributions from the html footer will violate the license of the theme? The theme is MIT licensed.
No. You are free to modify it, but include the license in the theme in your own theme. I recommend you copy the file with the attribution and license to your base layouts folder following the same path as the theme, and edit it there to avoid touching the theme.