@Physikerwelt. No, no. You (and also the WMF) are missing the point; this is not about the "individual" inconvenience. Personally I edit Wikipedia on my iPhone or iPad; with MathML with SVG, the math rendering is fast and looks good on my screen.

Here is another proposal: can we have MathML with fallback to MathJax? I understand the developers want MathML and the reality demands MathJax. Is there any technical obstacle to achieve this?

It is worth pointing out that MathML seems to have failed to get caught on as a markup language (in terms of browser support for instance). This is probably unfortunate; I can understand MathML is a better solution than more ad hoc approach like MathJax.