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will you tell me or let me discover it myself? :)

The correct way to is the compare the comment's id to its root_comment - if those numbers are the same, the current transaction in the block is a post; however, this requires getting the post content, which isn't so handy. @furion's method works without that.

thank you!

I usually just check for comment's parent_author, if it's empty, I presume I'm looking at a top level post