I once thought #durftevragen was a strong idea. You posted a public question on Twitter and knowledgeable people could reply even if they did not follow you. I sometimes saw useful answers arrive quickly. The hashtag took a question beyond your own network.
Why it worked
A good question made the need clear. People answering shared knowledge without needing to sell anything. That made the hashtag worth following: you could help someone and learn from other replies.
My original article also described businesses adding the hashtag to posts that contained no question. They wanted the same reach. Yet if followers see too much promotion between the questions, they eventually stop paying attention. Individual misuse reduces the reach that made the shared space valuable.
A lesson for any community
This is an observation from Twitter at the time, not a claim about today's algorithm. The wider lesson is that a shared convention works only when participants respect its purpose. Before using a popular tag, ask whether your post fits what people expect there. Ask a concrete question, add context and thank those who help. Promotion disguised as participation ultimately damages the place where you hoped to gain attention.