Does MS Office 2011 interface with High Sierra?

MS office 2011 was not designed to work with OS X HS and may or may not work or may not work entirely depending on your needs. Support for the product is the responsibility of Microsoft and they have since upgraded Office for Mac on more than one occasion to support the framework changes in OS X.

Microsoft Office support for macOS 10.13 High Sierra - Office Support

Sites like "roaring apps", etc. may tell you it works or does not however there are absolutely no guidelines for anyone to make any claim they want and no prerequisite of offer any proof to backup these claims.

Proceed at your own risk.

Because Office for Mac 2011 installs into System areas, an update to macOS High Sierra may stomp on some of Office's dependencies, and you may have to completely uninstall it, reinstall, and fully update (14.7.7) it. Be prepared for that surprise.

The principal message in the link provided by JimmyCMPIT is that Microsoft admits that they never tested Office for Mac 2011 against High Sierra, and now that this version of Office is officially unsupported, there will be no more updates from Microsoft to fix any issues that do develop. A properly updated Office for Mac 2011 may work fine for you on High Sierra, or it may not. There are reports here of both experiences. Any future update to High Sierra may permanently break the product.

For forward support and compatibility with future macOS offerings, I suggest that you use Office 2016 for Mac that is fully updated to 15.40 or later, and keep it updated.

Been using both Word and Excel (Office 2011) with HS and no issue so far but like others have said probably best to upgrade to Office 2016 so you have MS support in the future.