https://help.libreoffice.org/Calc/Spreadsheet_Functions#HLOOKUP Reason is that the wiki markup looks like that: See also:[[Calc/Spreadsheet_Functions|VLOOKUP]] (columns and rows are exchanged) as the link is on the same page, the linktext simply gets boldface. It would work if [[Calc/Spreadsheet_Functions#VLOOKUP|VLOOKUP]] or [[#VLOOKUP|VLOOKUP]] would look like.
Gabor Kelemen committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/help/commit/?id=e21bf9fa94cae8ec3527bed2aa6b4c71501b65eb tdf#97821 Add section anchors to VLOOKUP/HLOOKUP links