It's not an editor issue. It's about the ASP.NET globalization.

ASP.NET uses the UTF-8 character encoding by default when interpreting requests and composing responses. UTF-8 is optimized for the lower 127 ASCII characters, which means it provides an efficient way to encode languages that use the Latin alphabet. UTF-8 is also backward-compatible with the ASCII character encoding, meaning that UTF- 8 readers can interpret ASCII files.

To use the windows-1255 encoding, please modify your web.config file as followings:

<configuration>
  <system.web>
      <identity impersonate="true"/>
      <globalization
    requestEncoding="windows-1255"
    responseEncoding="windows-1255"
           fileEncoding="windows-1255"
           culture="he-IL"
           uiCulture="he-IL"
        />
  </system.web>
</configuration>