Don't know about finding corrupted tags but you can use the following regex to find any Chinese characters using MB's search & replace command:
Thank you. Your suggestion didn't help at first though. I realized that I had only my music library selected when making these queries. I didn't appreciate that <Moods> also included files still sitting in my inbox. So, when I added "inbox" to the source list, it showed up using your regex, mine (^[^0-9A-Za-z]) and a direct selection of mood itself.
So, basically, the key was to make sure that all libraries Musicbee sees (in my case, only two: the main one and inbox) are selected as sources for the autoplaylist,