rich_blocks turns markdown bullets into rich_text_list. rich_text does not interpret mrkdwn, so Slack <url|text> was emitted as literal text while [text](url) became a real link. Section/mrkdwn paragraphs were unaffected. Parse Slack autolinks in _inline_elements (lists, quotes, table cells). Mentions (<@U>, <#C>, <!here>) have no scheme: and stay as text.