@Physikerwelt is this still an issue? If so, what is the issue?

See https://www.mediawiki.org/w/index.php?title=Extension:Math/Roadmap&oldid=1248576

Double sub- oder superscripts: in $a^{c}}^{b}$ or $a_{c}}_{b}$ the b should be in a smaller font than the c. Applies to mixed cases as well. --Quartl (talk) 12:02, 1 November 2014 (UTC)

Thanks!

The examples in the page are weird. I suspect image for the a-b examples is stuck on an old rendering and that this is about a common point of confusion.

Here's a comparison.

Source:

<math>{x^2}^2</math>
<math>x^{2^2}</math>
<math>{x_2}_2</math>
<math>x_{2_2}</math>

Mathoid output:

LaTeX output (no extra packages):

I think that's a very good match. I'm guessing the OP was either about an issue that has been resolved or it was about the subtleties in the first and third example.

So I think this can be closed.