@Rémi Parmentier : ♬ YOU'RE SIMPLY THE BEST!!!!! (tam tam taaaaaam tam) BETTER THAN ALL THE REST!!! (tam tam taaaam tam) ♫ :D
I found (at least I think) a beginning of explanation: it only applies to celebrities with a Youtube, Deezer, Spotify or TuneIn account. If we try with Donald Trump or Denzel Washington, no underlining. But with Thom Yorke or Bruce Springsteen, there is underlining! Did you know that?