The first sentence is >If you're, for example, contributing to a reddit thread about something which is irrelevant or anything with only a short-term relevance

The first sentence is >If you're, for example, contributing to a reddit thread about something which is irrelevant or anything with only a short-term relevance, this article does not apply to you right now. Forums often end up with some posts that have a more long term benefit, and those should be hosted somewhere else.