You are missunderstanding Stéphane’s answer: he does not recommend you using a Windows server (actually we recommend NOT using a Windows server as OpenOLAT is not tested in a Windows environment and some file based operations are known not to work when using a Windows server).
However, when you want to fully support your Windows CLIENTS, E.x. XP, Windows 8 or 10, then you should run OpenOLAT in the ROOT context of your application server. This is because when you use the Windows native WebDAV client to mount OpenOLAT via WebDAV, Windows will run many WebDAV requests on the / of your server (/ = the ROOT context). If you are running OpenOLAT under a context path, e.g. /openolat/, then OpenOLAT can not respond to those queries and the Windows client might give up and can not connect.
This is the case for some versions and settings. Thus, to achieve best compatibility with Windows CLIENTS, you are advised to deploy OpenOLAT in the ROOT context.
Cheers