This is actually a widely known problem. Monospace text is too small in Firefox and Chrome. The problem is visible under the 'Help' button, 'What you type' column.
To trigger the proper textsize, a second, valid font is needed. So instead of { font-family: monospace; }, it should be { font-family: monospace, "Courier New"; }.
Note that this is not ment to prefer Courier New, but merely to provide a second, valid (and safe) parameter to trigger these browsers into displaying the correct fontsize. This means that any user's preferred monospace font will still be used.
There are two instances in jquery.wikiEditor.toolbar.css that would need to be modified: line 244 and line 270. In the latter case, line 271 (font-size) would no longer be needed and can be removed to ensure consistent behaviour between browsers.
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