Help for About Converting Microsoft Office Documents from https://help.libreoffice.org/Common/About_Converting_Microsoft_Office_Documents should be updated so that it can be used as a reference in different bugs.
1. There's "general overview of Microsoft Office features that may cause conversion challenges" but I hope they are not all there with LO 5.3.
2. For "Opening Microsoft Office Documents That Are Protected With a Password" PowerPoint is not mentioned at all and as Bug 33538 says: "Unable to open any password-protected PPT or PPS (PPTX and PPSX work)".
Open XML should be amended: "The Office Open XML format uses 128-bit AES encryption."