When you read a line of text, while your eye is taking in each word, your mind in interested in the periphery and preparing for what comes next. Our brains are good like that and peripheral vision comes in handy from time to time. In this case, when you track across a line and you come across a word that is unsupported by the text underneath, the mind assumes that this is the last line of a paragraph. However, this is not always the case. Microsoft Word and InDesign have a habit of leaving jumpers, or words hanging out on a line with nothing to support them underneath.
This is my own made-up term, but it seems pretty applicable. Like widows, orphans and bad-hyphens, fix them. Break them to the next line. Track the lines above and below to adjust them — not so much that it effects page coloration, but enough to remedy the rag (and every designer has their own rules for how far is too far).
If you can't do it with subtlety, try editing the text, adjusting the column or a myriad of other things... the point is: just take care of it.
[A natural line break (and paragraph end) on the right... and a jumper on the left.]