You've come to this page because you've hit problems caused by third-party Twitter mirroring into the FediVerse. This Frequently Given Answer explains what's going on.
The blurb for a piece of software named BirdSITELive encourages you to use other people's WWW sites that have it or set it up for yourself. On places like Hueyy's Awesome Mastodon it comes with a little fancy star next to it, unlike most other stuff listed. It must be a good thing, right?
It is not a good thing.
This is something that so many people who have used Twitter take as a short-term convenience, and that those new to the FediVerse see nothing wrong about. But for people who are already part of the FediVerse it in practice costs time, grossly misleads new people, and in extreme cases outright pushes away new people. It's commonly disliked, and the WWW sites that do it shunned.
The people who run the BirdSITELive software (or one of its derivatives) on their WWW sites have set up what is known as a third-party Twitter mirror. To the WWW sites on the rest of the FediVerse, this looks like a bona fide FediVerse WWW site. From the viewpoint of other FediVerse WWW sites, one can see accounts on it, follow them, and see posts made by them. The accounts have the same names and details as Twitter accounts, and the posts are posts that were in fact made to Twitter.
As a general rule, people in the FediVerse aren't setting out to make exact clones of Twitter et al.. The simple fact is that everybody who wants Twitter knows where it is, and can just use it directly. Mirroring Twitter into the FediVerse, thereby merely creating it all over again, is antithetical to what most people want to do.
This seems like a "gee whiz!" idea to people who want to see Twitter from the FediVerse, and don't initially think it through. But in practice this causes several sorts of problems:
Novices find these accounts when they search for people by name, start following them, and then get cross when they discover that they don't talk back and seemingly ignore all replies, mentions, and direct messages; or that they are even completely silent.
People find that reporting these accounts, for posts that violate FediVerse rules and norms, achieves nothing.
People joining the FediVerse from Twitter get upset that there seem to be hundreds of people "impersonating" them and complain loudly of an "impersonation 'bot problem" that they refuse to get involved with.
The real FediVerse accounts, of people who have both a Twitter account and a real FediVerse account, get buried in the search listings below heaps of fake third-party Twitter mirror accounts.
Sysops get complaints from irate people, about someone else's WWW sites, and have to waste time shunning and cutting off these WWW sites, in their hundreds, from their own systems. (This process is variously known as "limiting" or "silencing".) Novice sysops don't even learn that this is an issue until their first local user encounters it; and don't even know what resources for sysops exist about this.
Volunteers who welcome new people have to explain time and again not to follow these accounts. They have to explain repeatedly that only some parts of the FediVerse even see this stuff, thanks to the aforementioned "silencing", to confused users who get told that they are being "impersonated" by friends in other parts of the FediVerse. And there's no "FediTip", one of the more common volunteer-maintained resources for new people to the FediVerse, explaining this at all.
And some of the people whose accounts are mirrored get cross at this being done without their permission or even knowledge.
In fact, "impersonation 'bot" is not far from the mark, although the intent is not malicious and whatever "fake posts" being made are in fact genuine Twitter posts made from the original person. These WWW sites are not running FediVerse softwares like Mastodon or Akkoma et al., which allow real people to set up accounts. There's no person in the FediVerse posting to these accounts, and they aren't the people that they purport to be.
Rather, the whole WWW site is just a big robot, copying Twitter. There's no report handling system. Replies, mentions, and direct messages don't even enter into the picture, let alone get relayed back to Twitter. In the words of Roosta from the Hitch-Hiker's Guide To The Galaxy, "But there are no real people here at all!".
The first indicator that these WWW sites are poorly regarded is how many sysops "silence" them. You'll find them blacklisted in (just to pick two examples where the sysops clearly and publicly list them as as "Third-party bots") the moderated server list of Mastodon.Online and the moderated servers list of MastodonApp.UK, amongst many others. Check your own FediVerse WWW site's moderated servers list. These things might be already there.
Sysops have some resources, but even they don't learn about this straight away when they first set up their own WWW sites in the FediVerse.
There's a list of the sites, with a vague "you may want to block these" suggestion at joinfediverse.wiki but it is hugely incomplete and the list maintainer as of 2023 is unresponsive to reports of missing sites, of which there are hundreds not listed.
There's a longer list of the sites at ArtisanChat FediBlocks (by @Artifex@artisan.chat), with the much stronger "defederate on sight" recommendation, but it is dated November 2022.
Longer and more up-to-date lists are also published, with similar strong recommendations, as Oliphant.Social's BirdSITELive list (by @firstname.lastname@example.org) and Seirdy's list (by @Seirdy@pleroma.envs.net).
None of these are things to point a confused user to, though (except as proof that yes, many sysops actually do dislike these third-party Twitter mirror robots just like you do), because they are aimed at FediVerse sysops.