If your comment was blocked when you were trying to post it, then it would have been blocked by an automated system rather than manual intervention by a moderator. Human moderators simply cannot monitor comments live as they are posted - there are far too many of them.
Your comment may have included one or more words that can be used legitimately but that are also often used in an abusive or otherwise inappropriate context.
The original post in that thread didn't actually include any words other than the word "free" in the post title. "Free" obviously will not get flagged by the auto-mod, and neither will emojis.
The auto-mod is not smart enough to understand context. All it does is flag specific words. There is interest in AI-based moderation that understands context, but I have no idea if or when that will actually happen, and AI moderation also has significant potential to go astray (misunderstanding sarcasm, etc.).
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