This link https://projects.glasgow.social/rglasgow/ will let you enter a reddit username and it'll return a list of interests based on keywords in their post and comment history (if available). There is also a page that returns more keywords and tries to assign them a weight: https://starflyer.armchairscientist.co.uk/data/reddit/scan.php

It's far from perfect, but it does a few things to try and remove irrelevant words:

• Tokenisation - seperates the words by whitespace and removes duplicates
• Normalisation - ignores tokens that are too short (less than five characters) and too long (more than 12 characters - those are usually URLs etc)
• Stop word removal - Remove common stop words, based on this list of stop words.
• Lemmatisation - reduces (non-noun) words to their root origins