Quick answer: Unity TextMeshPro <b> and <i> tags rendering as plain text? Font asset's Atlas Render Mode = SDFAA doesn't include style variants - regenerate with bold/italic.
Chat with rich markup shows literal tags. Editor preview shows formatted.
Regenerate font atlas
Font Asset Creator. Include both regular and bold weights, plus italic skew. Atlas has the glyphs the markup expects.
Or use Style sheet
TMP Style Sheets define replacements (e.g., = brighter color). Simpler than full font generation.
Verify with rich-text test string
Render <b>Bold</b> and <i>Italic</i>. Both should style; literal tags = atlas missing weights.
“TMP rich text needs the font atlas to support the styles.”
If you use rich-text styles, validate the font atlas covers them. The default atlas is regular-only.