Fixed link to that style guide entry: https://guide.clojure.style/#opt-commas-in-map-literals

Per that style guide, the above map should be formatted like this:

  {:a 1
   2 :bar
   [1 2 3] :baz}

Most maps written in EDN have keys of a consistent type. A map whose keys are consistently keywords would look like this when formatted:

  {:a 1
   :bar "https://example.com/"
   :baz [1 2 3]}

Or like this, when condensed to one line:

  {:a 1, :bar "https://example.com/", :baz [1 2 3]}

The first map had keys of three different types: keyword `:a`, integer `2`, and vector `[1 2 3]`. Why would one want a format that supports maps with mixed-type keys? As a contrived example, mixed-type keys let you define a sparse 2D tile-based map for a game that is indexed by x and y coordinates:

  {:default {:type :grass}
   [0 1] {:type :npc-rival}
   [2 3] {:type :wall}
   [2 4] {:type :wall}
   [100 -5] {:type :treasure, :contents :sword-of-slaying}}

HN comment formatting help: https://news.ycombinator.com/formatdoc. I indented the above code by two spaces.

The confusion is that the order of the key and value can be reversed, and commas are optional, so there's no way to tell at a glance what e.g. the value associated with:bar is.

>the order of the key and value can be reversed

This is the case with any hash-map in any language, modulo some of them making certain keys illegal.

But "string":"string" can be reversed in pretty much any language's hash-map.

>here's no way to tell at a glance what e.g. the value associated with:bar is.

You've certainly constructed and formatted a hash-map that is a little tricky to understand, but 1> this combination of key and value types is going to be pretty rare in the wild and 2> to the extent it exists, people would format it to be easier to parse, either by adding commas or newlines.

> the order of the key and value can be reversed

That's not true. What you're seeing here is a map where [1 2 3] is the key for the value :baz