It seems that I can't use any other syntax inside headlines. Is this a bug?

No, it's not a bug. It's a limitation of how headlines work in DokuWiki. There are two reasons:

1. From a typographic view it's considered bad style to have any formatting in headlines.
2. The headlines are used in theTOC and some other places as well, doing this with markup in between would be technically very complicated and error prone.

A more detailed technical explanation is available in thismailing list post.

But what about typographical entities (like em-dash, copyright symbol, curly quotes, etc.)?

You can include any special character into the headings.Typographic conversions don't work in headings but adding the resulting characters directly works. You can use the character picker () in the editingtoolbar to do that.

But what about illustrating a headline with an icon or making it italic?

General styling can still be done withCSS, including icons, italics, backgrounds and color. Seehow to style headers with use cases and pictures.

TheCombo plugin authorizes other formatting syntax natively in itsheading component. You can add an icon or any formatting syntax such as bold, italic and more.

If you really want to insert wiki syntax in the header, try pluginHeader2.

The pluginHeader2 (andHeader3) became unavailable due to a technical reason (See this conversation). You can consider usingWiki-Style Script, which applies wiki syntax ofbold, italic, underlined, or monospaced text if they are remaining (such as those in headers and link texts). You can alsochange color of characters in headers and link texts.