If a paragraph has some override(s) in it that do not affect the entire paragraph, you'll see the little paragraph symbol at the bottom of the panel light up. This tells you there's an override. No + sign will appear next to the paragraph style name, though, unless the cursor happens to be in text that has the override. For example, if one word is in italics but your cursor is elsewhere in the paragraph, you don't have any way to know what the override is. If you select the entire paragraph, the + appears, but when you hover over the style name the little message that pops up ALWAYS says "mixed overrides," even if there is only one override. Only if the override applies to the whole paragraph will the message be informative.
I know I can turn on the blue override highlighting, but that's not always what I want to do as it's distracting and ugly, and sometimes I have lots of intentional, temporary overrides that would also be lit up.