No benefits to making it public, only downsides.
First and foremost, the message would reach less than 1% of the target audience. You think I don't know what mangadex looks like? I do, so do almost all of its users. The people who would benefit from the announcement are the ones who will never see it. (the hopefully <1% here are our technologically impaired users. Who are probably on the phone right now paying "microsoft" $3.99 to unlock their computer since they have a virus message on google chrome)
As far as the downsides for advertising for them go, well... there you have it. All we would be doing is advertising them, and ads are beneficial regardless of what kind of light they are in. A link on the front page would not only encourage our users to visit the site (out of curiosity), but also promote the site on search engines (its like telling google mangadex recommends enemyA). What more, our curious users clicking on the link would also likely increase their ranking in search results. Would they overtake mangadex? Not even close, but there are no foreseeable benefits to moving this low ranked enemy up a few notches in google just for fun.
The very most we should say is "Look out for imposture sites. Make sure it says https://mangadex.org in the address bar when you visit our site". It won't help worth crap, but it shows you care to the 99% of users with a brain.
