sandbox for example: https://ru.wikipedia.org/wiki/%D0%98%D0%BD%D0%BA%D1%83%D0%B1%D0%B0%D1%82%D0%BE%D1%80:%D0%9F%D0%B5%D1%81%D0%BE%D1%87%D0%BD%D0%B8%D1%86%D0%B0?setlang=en
in wikitext may be a lot of invisible templates
invisible also in the visual editor
invisible templates need to show such as invisible comments
examples of invisible templates (ru:Template)
Link FA, LinkGA, LinkLA, bots (bots|deny=Dibot), "Template:^", Coord, and other
they exist in the text
can not see them
they accidentally deleted