Structured threads vs an unending ticker tape of noise.
This article is really, "We couldn't adapt our processes to Slack, so we blamed the tool and replaced a chat app with processes, because we're special snowflakes and how could anything Not Invented Here apply to our totally unique problems of communication?"
Sure, they ended up with a series of other tools to cover their workflows, the thing they "invented" was how those tools work together to cover the gaps created by not actually having a comprehensive and well-configured chat app.
IMO just use forum software if you're going that way. Much more low volume, too (generally).
Further, "optimize for searching" isn't a thing. Teams gives full text search, and you can find any word or phrase you need to instantly.
I think you're optimizing for familiarity.
For example https://chat.zulip.org/#narrow/stream/3-backend/topic/Vagran...