Maybe I misunderstood your original post, I thought you meant your comments here on HN, not a personal website you control.

Others have said it already but when you are posting here on a public website, I would argue that you are effectively consenting that your content is now available for consumption by site visitors.

"Site visitors" may include people, systems, software, etc..

I think it would be pretty impractical for every visitor to the site to have to seek consent from each poster before making use of the content. That would literally break the Internet.

Which search engines are you in that you didn't opt into?

My website currently shows up on bing (which has an opt-out tool, I just haven't bothered to use it), duckduckgo (which scrapes its results from other engines) and yahoo search (which apparently scrapes from bing). I can't check Kagi as I'm not paying for it, and I can't currently think of other search engines off the top of my head