RadEditor Classic does not support the modern browsers and the reported problem could be due to that. Its development and support is discontinued since 2008 and for this reason it is highly recommended to migrate to the new and much enhanced RadEditor for ASP.NET AJAX. Upgrading instructions are provided in the following help article: Migration from RadEditor Classic to RadEditor for ASP.NET AJAX
The face="AZBY" problem is also fixed in the new version of the control.
The only thing that you can try before considering to upgrade is to replace the FontSize tool with the RealFontSize
tool of RadEditor Classic and see whether this will fix the font size issue.
the Telerik team
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