This is one of slack's weak-points imo. Discord allows you to reply to a particular message when making a post. In Slack you make a "thread" but then click "also post in channel". This can cause a lot of confusion if all you're trying to do is use it as a reply because most people will start replying to the thread, not realizing you were trying to keep the conversation as part of the regular channel flow

Slack buries threads at the surface level. This is helpful in some situations but can lead to a lot of confusion