This breaks that <config>-ThornGuide target with

! Undefined control sequence.
l.42427 {\bf Title:} & \thornname
                                  \\
? 
! Emergency stop.
l.42427 

new macros must be defined inside of the magic comments ideally just below the comment % Add all definitions used in this documentation here which the documentation template contains.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2828/wvuthorns_diagnostics-defines-new-macro