> Anki can help you identify leeches. Each time a review card 'lapses' (is failed while it is in review mode), a counter increases. When this counter reaches 8, Anki tags the note as a leech and suspends the card. The threshold, and whether to suspend or not, can be adjusted in the deck options.

> If you keep failing that card, Anki will continue to alert you about the leech periodically. These warnings occur at half the initial leech threshold. For example, if you set the warning at 8 lapses, future warnings will happen every 4 lapses (at 12, 16, and so on).

Suspend means you never see the card again. So how could you keep failing it after it's been suspended for being a leech?

You need to mark that card with lowest recall for leeches to happen. If you mark it with second lowest one, it won't become leech.

If it becomes leech, it will be ignored entirely by anki.

All of that is too much expertise about how to mark cards instead of allowing you to do it intuitively.

The leech feature can also be dangerous if you're unaware of it, because AIUI Anki does not ask you whether to remove a difficult card or not, it just goes ahead and does it.

That's true, though the stats screen will tell you how many suspended and buried cards you have. If I track that a few times a week I can usually tell when something has been suspended that I didn't suspend myself.