Hello Dilyan,
I can't opening your project because I'm using VS 2010 and it's incompatible.
In my .Xaml, I'm using neither styles targeting the FontFamily nor apply a 'Font' properties (like color, size, etc...). I'm using the default values.
I tried your code :
<Style x:Key=
"cellStyle"
TargetType=
"telerik:GridViewCell"
>
<Setter Property=
"HorizontalContentAlignment"
Value=
"Center"
/>
<Setter Property=
"FontFamily"
Value=
"Consolas"
/>
</Style>
// I added your FontFamily setter.
-> The font is applied but the black special character with '?' is always presents.
I noticied that when I edited cell, the accent is applied (attached file).
Resume :
=> When data is loaded, accent isn't here.
=> When data is added by editing, accent is presents.
Thank you for your answer.