Keyword there I think is "runs of phrasing content". That means that you can "nest" different tags but not those of the same tag. The nesting <b> inside <b> lik

Keyword there I think is "runs of phrasing content". That means that you can "nest" different tags but not those of the same tag. The nesting <b> inside <b> like op is causing the parser to ignore the depth of nesting of <b> elements and just closes the bold content on first </b>.