@seindal @renes-old-blog damn, that sucks! Sorry to hear that.
If you're on iOS, I'd consider using something like @Mona or @IceCubesApp that have this feature to shorten posts with an option to expand.
If you're on Android, I'd consider using @moshidon or @megalodon
If those don't look like apps you'd enjoy, I'm out of ideas because this is strictly a Mastodon issue. They don't allow "article" type posts which are how WP defines them. I don't see this changing anytime soon but you can request a feature on their roadmap page: https://joinmastodon.org/roadmap