I now have a massive discrepancy (20% size change) between font size normally displayed on a page and font size in the edit window.
To clarify: I edit on both PC (Windows) and Mac (OSX), and this issue affects both. The two systems are on different networks. I use Firefox nearly all the time, but find the problem exists in Safari as well. I have access to large screen monitors, and have set my font to display for preferred readability, but as of about a week ago I now get a severely reduced font size when I open an edit window. It is so small that I cannot read it without enlarging the font size two steps in my browser, and so I estimate the edit window is displaying about 75-85% of the size in regular display.
This issue affects all MW projects. It is not skin-specific, as I have tried several skins now.
The issue appears in serif fonts, but not in monospaced fonts. For Wikipedia editing and Commons editing, monospace edit font is a workable solution, but for Wikisource it is not. Why? First, on Wikisource proofreading is side-by-side comparing contents of the edit window against a source text, which is almost always in a serif font. Having the contents of the edit window in a similar font to the comparison text makes the job many times easier. Secondly, I work primarily with bilingual texts where the second language (Greek) is not written in the Latin script. Polytonic Greek script is virtually unreadable in a monospaced font. So I need to use a Serif font for that reason as well.
And while I have managed for a few days by repeatedly scaling the browser font size up and down every time I go in or out of edit, preview a text, etc., I find that this is definitely NOT a long-term solution.
If this issue cannot be resolved I will have to give up editing on Wikisource. I am getting older, and my vision cannot cope with the tiny script. Toggling the font size in the browser is cumbersome and has caused me to lose significant work more than once because of the differences between my PC and Mac keyboard commands and the difference in scrolling directions. I have ended up leaving pages instead of adjusting the font size.
It baffles me that after all this time there is no "Preference" allowing a user to adjust their font-size in the edit window.