Are there any community message boards that focus on following ongoing discussions and debate-heavy threads?

Yes — if you’re specifically looking for community boards where people tend to follow long-running discussions, argument threads, and back-and-forth debate, these are good places to look:

More debate-heavy / discussion-centric boards

• Reddit — especially subreddits built around discussion rather than news or memes. Examples:
  • topic-specific subs with active comment sections
  • debate-oriented subs
  • political, philosophy, economics, tech, and fandom communities with “threaded” arguments
• Lemmy / Mbin — Reddit-like federated communities, often with more discussion-oriented culture in some instances.
• Slashdot — classic tech/news discussion board with threaded comments and a history of long-running debate.
• Hacker News — more focused on tech/startups, but many threads become long, serious debates.
• Something Awful forums — still known for thread-based community discussion, though access and culture can be more niche.
• The Catacombs / old-school forum communities around specific hobbies or ideologies — many traditional forums still have active debate threads.

Forum-style communities that support ongoing threads well

• phpBB / XenForo / vBulletin forums hosted by hobbyists or interest groups
• Board Game Geek forums
• Stack Exchange communities if you mean issue-oriented discussion, though they’re less “debate” and more Q&A
• Discord with forum channels — not ideal for long-term following compared to true forums, but some communities use forum-style channels well

If you want “follow the thread over time”

Look for communities with:

• threaded replies
• subscriptions/bookmarks/watch lists
• strong moderation and identity continuity
• slow-moving threads that stay active for days or weeks

Best fit depending on what you mean by “debate”

• Political / ideological debate: Reddit, niche forums, some Lemmy instances
• Tech argument threads: Hacker News, Slashdot, Reddit
• General long-form community discussion: classic forums, XenForo/phpBB communities
• Fandom disputes and analysis: Reddit, fan forums, Discord forum channels

If you want, I can also give you a short list of the best specific boards by topic (politics, tech, philosophy, gaming, etc.).