Posted by Andrew Carver on Oct 04, 2018; 4:18am
URL: https://discuss.asciidoctor.org/How-to-add-markup-to-author-information-in-document-title-tp6488p6490.html

This seems to work:

= A Trademarked^(TM)^ Title
:R: pass:q,r[^(R)^]
Editors: A Registered{R} Editor

I think this issue is due to it being in a header--where, if I gather correctly, only "Special Characters" and "Attributes" get replaced. But having an attribute entry above the author line doesn't disrupt; because, "Attribute entries can be placed anywhere in the header" (https://asciidoctor.org/docs/user-manual/#doc-header).