The W3C example image is incorrect; small tilde
must be stretchy.
Stretchy accent test
<math xmlns="http://www.w3.org/1998/Math/MathML"> <mover> <mi>xxx</mi> <mo>ˆ</mo> </mover> <mo>+</mo> <mover> <mi>xxx</mi> <mo>¯</mo> </mover> <mo>+</mo> <mover> <mi>xxx</mi> <mo>ˇ</mo> </mover> <mo>+</mo> <mover> <mi>xxx</mi> <mo>˜</mo> </mover> <mo>+</mo> <mover> <mi>xxx</mi> <mo>⏞</mo> </mover> <mo>+</mo> <munder> <mi>xxx</mi> <mo>⏟</mo> </munder> <mo>+</mo> <mi>xxx</mi> </math>
Author: Design Science, Inc. (D. Doyle, R.Miner)