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).

It does a few things to try and remove irrelevant words:

• Tokenisation - seperates the words by whitespace and removes duplicates
• Normalisation - ignores words 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