Syntax discussions tend to be highly contextual. The syntax of a language is not a standalone, separate entity, but rather interacts with what type of algorithmic solutions you envision users to employ. On top of that, one must be aware of that syntax shapes the solutions users will prefer in sometimes unpredictable ways.
This makes completely new syntax very hard to analyze. And also hard to write any guidelines for.
That said, I think there are some things we can say about syntax design, to form some very simple (and obvious) guidelines:
- In general, an easy-to-parse syntax tend to be easier for a user to read quickly than a complex-to-parse syntax.
- Newly invented syntax will initially be harder for people to grok than established syntax. So it is bad if you try to make experienced programmers understand it "at a glance".
- Newly invented syntax does makes the language feel more "different" (unique, inventive etc) than established syntax. So it is good if you want to make the language stand out as being different at a glance.
- It's harder to know the downsides of newly invented syntax. So much more research is needed, and it's important to be ready to change it down the line if it doesn't work out.
- One's personal opinions of what "nice looking syntax" is very unlikely to be the objectively most accurate opinion, so be aware how that "beautiful" syntax might be hideous to someone else.