LO 3.4.5/3.5.1 for windows ignores decimal separator settings from OS locale settings.
For example, I use windows locale set to russian.
Default decimal separator for this locale set by Microsoft is a comma, but in reality most times this decimal separator is modified to be a dot.
LibreOffice completely ignores modified locale settings and always sets decimal separator to a comma.
The only workaround is to change language in LO to German(Switzerland) or UK. This depends on date format settings you want to get.
I can confirm this happens under Windows XP Pro x86. I have the same problem.
It is not that locale is ignored. Locale is enforced. It's the customized settings that are ignored.
Apparently LO doesn't expect customized settings.
There currently is no system layer for locale data to merge in OS settings that vary from the locale's settings. This needs to be implemented.
*** This bug has been marked as a duplicate of bug 46448 ***