In section 23.5.6 the text: "With -Ui, mergemaster(8) automatically updates files that have not been user-modified and installs new files that are not already present: # mergemaster -Ui" There is no -Ui parameter to mergemaster. It should presumably read just "-U" and not "-U1".
Oops - this seems to be a font problem with the "# mergemaster -Ui" appearing as "# mergemaster -U1" in the SeaMonkey web broweser, but correctly as "# mergemaster -Ui" when cut and pasted into the bug report.
Created attachment 184467 [details] SeaMonkey screen dump extract
It is very curious that the 'i' has a serif when after 'U' or 'f', but after (e.g.) 'w', there is no serif. Nonetheless, this seems to be a rendering issue specific to SeaMonkey, as I do not see it in my local Chrome. So, I'll have to close this ticket, as there is no issue with the documentation source itself.
I tracked the font rendering problem down to the font used for monospaced text (Andale Mono). When changed to Bitstream Vera Sans Mono, the text rendered correctly. Added resolution should anyone else suffer a similar issue.