Not sure where anything in that link contradicts what I said. A character used in a logo is one of those cases where a character is used as a trademark, but it only applies to that logo. Having a trademark of a Mario logo wouldn’t mean that Mario couldn’t show up in works that aren’t by Nintendo, it’s purely the copyright that prevents that.

The part where it gets complicated is more about, for example, a video of Mario playing Palworld and saying “This is-a better than-a pokemon!” was used to try to imply Nintendo themselves recommended Palworld over Pokemon, since Mario is a trademark of Nintendo and strongly associated with them.

Trademarks are about marketing and the origin and/or endorsement of something. Copyrights are about the presentation and creative use of the copyrighted works.

That said, if trademarks are used in the creative work, it seems as though they would need to be removed for someone else to sell that work. So if steamboat Willie has the Disney logo as a part of its opening credits and someone else tries to show it without removing that logo, Disney world likely have a trademark infringement case. But they wouldn’t have a case simply because Mickey mouse could be considered they spokesman and is a character in it.

For the Nintendo ones, once super Mario Bros’ copyright lapses, “Super Mario” might need to be removed from the title for others to sell it to avoid infringing on Nintendo’s trademark. But the characters of Mario, Luigi, Mushroom Man, King Koopa, and the Princess would be fair game, either in the game’s original format or derivative works.