Why is whitespace sometimes needed around metacharacters?

Just tattoo a

#!/bin/zsh

shebang above it and you'll be fine.

Braces are more like odd keywords than special symbols, and do need spaces. This is different to parentheses, for example. Compare:

(ls)

which works, and:

{ls}

which looks for a command named {ls}. To work, it has to be:

{ ls; }

The semicolon stops the closing brace being taken as a parameter to ls.

All you have to do is tell people that you are using a proportional-font with a rather narrow space character.

There is a list of characters that separate tokens in BASH. These characters are called metacharacters and they are |, &, ;, (, ), <, >, space and tab. On the other hand, curly braces ({ and }) are just ordinary characters that make up words.

Omitting the second space before } will do, since & is a metacharacter. Therefore, your tattoo should have at least one space character.

:(){ :|:&};: