↑ ↑ ↑
Not seen it since I banished it on day two of using calibre, with one exception - I show it in my Test library, which I switch in and out of frequently.
However, I control what columns I see with the View Manager plugin, occasionally I right click the headers to show a column I don't normally see - such as modified date and size, but not rating.
Off hand I can't even think of a key sequence to toggle show/hide a specific column in the book list.
Afterthought : what about metadata downloading, could that trigger it (wouldn't have thought so, but...), I have rating unchecked both generally, and for each source.
BR