Copy-paste this script in your browser console to load all comments on that reddit thread. (added resume after some time as well as a way to pause all downloads)

load_all_reddit_comments.js

pause = false, timeout = lastFetch = restarter = null, moreCommentSelector = 'span.morecomments > a'

 moreCommentLinks = () => document.querySelectorAll(moreCommentSelector)

 showProgress = msg => {
 	lastFetch = Date.now()
	console.log(`${new Date().toLocaleTimeString()} — ${msg}`)
 }

restartIfPaused = () => {
	if(!pause && moreCommentLinks().length && ((Date.now() - lastFetch)/1000 > 20)) {
		loadMore()
		console.log('Resumed loading new comments...')
	}
}

clearAllTimers = () => {
	clearTimeout(timeout)
	clearInterval(restarter)

	pause = true
	
	console.log('Timers cleared.')
}

restarter = setInterval(restartIfPaused, 30000)

 loadMore = () => {
	timeout = setTimeout(() => {
		if(!pause) {
			let links = moreCommentLinks()
			links[0].click()

			let remainingLinks = links().length - 1
			showProgress(remainingLinks)
			
			remainingLinks? loadMore() : clearAllTimers()
		}
	}, 5000)
}

loadMore()