I think better advice is to know your message, know your audience, and write appropriately. If you're skilled enough to write flowery prose in the first place,

I think better advice is to know your message, know your audience, and write appropriately. If you're skilled enough to write flowery prose in the first place, then you're skilled enough to detect the appropriate level and write to it. For example, there is a world of difference between troubleshooting a user problem verbally, directly in email, or writing a guide for the problem on a wiki. They all take different conversational styles.