When an article is published with the Online Editor disabled, we see that on the front-end, all the paragraphs have disappeared.
This does not show up in the back-end editing interface, where it looks like all the paragraphs are still there.

Clue: publish a multi-paragraph article with the Online Editor enabled, and the paragraphs get stored like this:

<paragraph>some text</paragraph>

With the Online Editor disabled, paragraphs get stored like this:

<paragraph xmlns:tmp="http://ez.no/namespaces/ezpublish3/temporary/">some text</paragraph>

Update: Paragraphs are stored like this in both 5.4 and 5.3, but the bug only occurs in 5.4. This is because it is triggered by EZP-23513, which introduces a change in XSL templates causing the temporary namespace to not be rendered anymore.