[ksa]

Как вариант...

<form id='commentform'>
	<button id='submit'>Тест</button>
</form>
<script>
document.querySelector('#commentform').addEventListener('submit', _ => {
	_.preventDefault()
	const o = document.querySelector("#submit")
	o.value = 'Отправка комментария...'
	o.disabled = true
	const html = '<div class="comment-spinner" style="padding-left: 20px; cursor: wait;">comment-spinner<div>'
	o.insertAdjacentHTML('beforebegin', html)
})
</script>