It's perfectly acceptable to take reports from trustworthy sources as fact. Further, it's equally acceptable to give credence to so-called ITKs on here who confirm it.
But people have different ideas of what is "confirmed".
@TFC doesn't believe a word until a player holds up a City shirt on the OS. You, however, were more than willing to take
@MCRJON at his word that Walker was done, never mind what's going on with Ederson.
Some people won't believe it no matter what, but the majority on here aren't so sceptical. I'd say those going into a frenzy over a Telegraph article retweeted by City Watch are in the latter category and suggesting, then, that there's far more reliable sources stating Mendy is a done deal, is fair game.