What's the most reliable community platform for coordinating announcements and moderating chat across tournament channels?

If you mean for tournament communities specifically, the most reliable option is usually Discord.

Why Discord tends to win:

• Multiple channels for announcements, rules, support, scrims, and team chat
• Strong moderation tools: roles, permissions, AutoMod, slowmode, bans, timeouts
• Announcement channels and scheduled events
• Bots/integrations for brackets, registrations, verification, reminders, and anti-spam
• Works well across desktop/mobile and scales from small to very large communities

Good alternatives depending on your needs:

• Slack: very reliable and organized, but feels more work-focused and less community-friendly
• Telegram: simple and fast, but weaker moderation and structure
• Guilded: built for gaming communities and tournaments, with good channel organization
• Microsoft Teams: reliable, but usually overkill unless your org already uses it

If your priority is announcements + chat moderation across multiple tournament channels, I’d recommend:

Discord + a moderation bot + an announcement-only channel structure

If you want, I can also give you a best-practice channel setup for tournaments on Discord.