I just noticed in passing that MathJax alignment in this answer has become very ugly - see the excerpt below. The string of $x$'s is wavering up and down. I don't recall seeing this when the answer was composed. MathJax 2.7.0, Chrome v54.0.2840.59 — woff or otf fonts, Win7 Pro 64b. The problem does not occur in the latest version of FireFox in the same environment, so it may be Chrome specific.
Update Another datapoint: my Zoom was at 90% in Chrome, so the bug may depend on that (reproduced by DanielR at 90% and 125% Zoom - see comments). At 100% Zoom there is no problem. FireFox looks ok at all zoom levels.