In multilanguagal wikis (e.g commons, wikidata) and in somewhat lesser degree in other wikis, we can't have strict assumption on the language direction - e.g in Wikidata/Commons it is reasonable to have discussions in Arabic/Hebrew. Specially in flow posts, we can take advantage of it's structure and add dir=auto

For example: where we can benefit of it - discussion between to RTL speakers in Wikidata: https://www.wikidata.org/wiki/Topic:Upx7qlekfqlwlpz1