Forth is not under the radar in any sense. It is much more popular and well known than any underground band.
I can definitely think of underground bands more popular than it and significantly more well known than it despite still being absolutely under the radar, because it only has, upper bound, ten thousand people who actually program in it. That's basically a single college radio station play's worth.
You're conflating "I read this" with "The world reads this." This is a common error. The trick is to realize that your experience with the internet is not universal, and that it is unlikely you are the average user in any group you're in.
Further, it doesn't even show up on the subreddit you mention very often; I just checked the reddit BigQuery database and FORTH posts don't collect a portion of upvotes worth mentioning in any given year.
Also: Using superfluous question marks for emphasis is a reddit habit. It should not be done on HN, because it is annoying and lowers the quality of discussion; the guidelines forbid uppercase-emphasis for this reason, and this is more egregious.