If I had to guess, I'd say that the other topic was locked because A) the original post is 4 years old, B) Microsoft (specifically the developers of the Windows Desktop Search feature) isn't giving an answer other than that the errors are harmless,
so you won't be getting anything from them, and C) half the posts were about operating systems other than Windows Home Server. But I can't say for sure, as the forum software doesn't show me a reason for the lock.
What I think the error is really telling you is that there is a file type in an indexed location which the search service doesn't know about. You can add these file types, however doing so is technically unsupported and it's completely unnecessary,
since these errors don't indicate anything is actually wrong. Why the developers of WDS chose to make them errors rather than warnings is a topic for another day, and another forum...
I'm not on the WHS team, I just post a lot. :)