In reading mode fonts much less readable at large distances than in edit mode. As if under some effect of smoothing. Because of this eyes get tired very quickly and you have to constantly zoom in and out.
Please resubmit this bug report and make sure that: 1) you follow the bug report template, 2) you use the default theme (no css) and 3) there are no third-party plugins enabled (You can use the sandbox vault for 2 and 3).