Originally posted by FissionChips:

In short multiplayer in Valheim is designed for friend groups, not public servers.

A very good point; it's better with people you trust not to grief.
The "Greater Internet F-Wad Theory" excludes randos in multiplayer by default, as do the default settings when creating a Valheim server from the in-game menu.

See this Penny Arcade webcomic from 2004[www.penny-arcade.com] (NSFW, language)