Some stuff can't be fixed on LibreOffice, let's try to list them and explain why.
convert_add function from "at" or "atm" to "Pa" gives same answer
tdf#72174 gives details but in brief, "at" and "atm" are 2 different units whereas LibreOffice consider them as same unit. This is due to 2 things:
- the will to be compatible with Excel which treats them as same unit too
- the fact that odf standard has followed this Excel's error
ODF standard should be fixed in its version 1.3 (https://issues.oasis-open.org/browse/OFFICE-3851)
Missing right parenthesis isn't detected in Basic
First a bug, tdf#80731, has been declared for this and it's been fixed. Then tdf#106529 has been declared because lots of macros suddenly triggered errors. Even if most of (all?) LibreOffice macros have been fixed for the missing right parenthesis, any extension or macro used in companies may trigger this error. So the initial fix has been removed.
Some code refer to "Persistant" whereas right spelling is "Persistent". This can't be fixed because has been declared as public interface and thus would break API compatibility (see http://opengrok.libreoffice.org/xref/core/offapi/type_reference/offapi.idl#4315 and https://gerrit.libreoffice.org/#/c/35096/)
Some code refer to "THROUGHT" whereas right spelling is "THROUGH". it's been fixed in 5.4 version and for the moment the wrong spelling has been deprecated, see https://cgit.freedesktop.org/libreoffice/core/commit/?id=8913353a8fd2a1d281c2d8a33ca795d97201b7bc