Most likely that character has a different encoding than the remaining blog. UTF vs ASCII vs Unicode, all different.
I've been around spreadsheets/databases/flat files forever to see this happen more than you'd expect.
It's directly a result from the original composition, perhaps taken from different sources, then copied to a new platform. Copied again and perhaps again.
Unicode usually screwed up a lot of databases. It can be fixed by running the blurb through Notepad++ but most wouldn't care to so it results in garbage in, garbage out.