The following code using go 1.13.3 misplaces HeadComment entries to the underlying node (but not consistently). In particular, head comments in lists of lists items are moved as head comments in each sublist's first node, whereas head comments in normal list items are not consistently preserved (e.g., see the difference between comment 3 and comment 4 in the snippet below)

The following code

package main

import (
	"fmt"
	"log"

	"gopkg.in/yaml.v3"
)

var (
	sourceYaml = `
l:
  # comment 1
  - - a
    - b: "2"
    - v
  # comment 2
  - - k
    - m
    - v
  # comment 3
  - a
  # comment 4
  - b: "2"
`
)

func main() {
	yamlNode := yaml.Node{}

	err := yaml.Unmarshal([]byte(sourceYaml), &yamlNode)
	if err != nil {
		log.Fatalf("error: %v", err)
	}

	out, err := yaml.Marshal(&yamlNode)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(string(out))
}

yields

l:
  - # comment 1
    - a
    - b: "2"
    - v
  - # comment 2
    - k
    - m
    - v
  # comment 3
  - a
  - # comment 4
    b: "2"

Thanks for the report. I'll have a look into it.