A related-posts block helps when it surfaces genuinely adjacent content, and turns into noise the moment it becomes automated filler that ignores relevance. The deciding factor is not whether the block exists but what fills it: a curated set of truly related articles does real work, while an algorithm padding the slot with whatever shares a tag or category mostly adds clutter.
When the block is curated and relevant, it pulls its weight in two ways. For readers, it offers a natural next step, which keeps them on the site and moving through related material. For search engines, it distributes internal link value toward the posts you actually want supported and reinforces that those pages belong to the same topic. A block at the end of an article that points to three posts a reader of this article would plausibly want next is functioning as a genuine internal link, not decoration.
It tips into noise when relevance drops out. An automated widget that fills its slots by recency or by loose category overlap will link a post about one subject to four posts about something only vaguely connected. That weakens the topical signal rather than strengthening it, spreads link value across pages that do not deserve it, and trains readers to ignore the block because its suggestions are rarely useful. There is a technical cost too: related-posts blocks generated dynamically in JavaScript can be harder for Google to see and follow than links written into the page, so a block that looks full to a visitor may pass little to a crawler.
Judge your own block by reading it as a visitor. Look at the suggestions under a few of your posts and ask whether you would actually click them given what the article was about. If most are tightly related, the block is helping. If they feel random or repetitive, the widget is padding the page, and it is worth switching to curated suggestions or tightening the relevance rules rather than leaving it to fill slots on its own.