Hi,

A couple of things to try;

[TinyMCEPluginNonVisual(ServerSideOnly = true, AlwaysEnabled = true, EditorInitConfigurationOptions = "{ extended_valid_elements: 'section[class|id],script[type],iframe[class|src|frameborder=0|alt|title|width|height|align|name],svg[*],path[*],line[*],circle[*],g[*],polygon[*]'}", PlugInName = "TinyMceExtendedValidElements")]
public class ExtendedValidElements
{
}

1. I don't know if you have a plugin script as well, otherwise you'll want to add ServerSideOnly = true
2. According the specs over at tinymce, elements in extended_valid_elements should be separated by comma(,) and not pipe(|)
3. You shouldn't need to change episerver.config since that is the default values of mergedConfigurationProperties

/Erik

Thanks.

 I have tried your suggestion but it doesn't seem to work unfortunately. Still strips out the inline SVG.

Could you post an example of the svg you try to include?

/Erik

I have tried several, but for example this one from http://css-tricks.com/using-svg/:

<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
   width="612px" height="502.174px" viewBox="0 65.326 612 502.174" enable-background="new 0 65.326 612 502.174"
   xml:space="preserve" class="logo">

<ellipse class="ground" cx="283.5" cy="487.5" rx="259" ry="80"/>
<path class="kiwi" d="M210.333,65.331C104.367,66.105-12.349,150.637,1.056,276.449c4.303,40.393,18.533,63.704,52.171,79.03
  c36.307,16.544,57.022,54.556,50.406,112.954c-9.935,4.88-17.405,11.031-19.132,20.015c7.531-0.17,14.943-0.312,22.59,4.341
  c20.333,12.375,31.296,27.363,42.979,51.72c1.714,3.572,8.192,2.849,8.312-3.078c0.17-8.467-1.856-17.454-5.226-26.933
  c-2.955-8.313,3.059-7.985,6.917-6.106c6.399,3.115,16.334,9.43,30.39,13.098c5.392,1.407,5.995-3.877,5.224-6.991
  c-1.864-7.522-11.009-10.862-24.519-19.229c-4.82-2.984-0.927-9.736,5.168-8.351l20.234,2.415c3.359,0.763,4.555-6.114,0.882-7.875
  c-14.198-6.804-28.897-10.098-53.864-7.799c-11.617-29.265-29.811-61.617-15.674-81.681c12.639-17.938,31.216-20.74,39.147,43.489
  c-5.002,3.107-11.215,5.031-11.332,13.024c7.201-2.845,11.207-1.399,14.791,0c17.912,6.998,35.462,21.826,52.982,37.309
  c3.739,3.303,8.413-1.718,6.991-6.034c-2.138-6.494-8.053-10.659-14.791-20.016c-3.239-4.495,5.03-7.045,10.886-6.876
  c13.849,0.396,22.886,8.268,35.177,11.218c4.483,1.076,9.741-1.964,6.917-6.917c-3.472-6.085-13.015-9.124-19.18-13.413
  c-4.357-3.029-3.025-7.132,2.697-6.602c3.905,0.361,8.478,2.271,13.908,1.767c9.946-0.925,7.717-7.169-0.883-9.566
  c-19.036-5.304-39.891-6.311-61.665-5.225c-43.837-8.358-31.554-84.887,0-90.363c29.571-5.132,62.966-13.339,99.928-32.156
  c32.668-5.429,64.835-12.446,92.939-33.85c48.106-14.469,111.903,16.113,204.241,149.695c3.926,5.681,15.819,9.94,9.524-6.351
  c-15.893-41.125-68.176-93.328-92.13-132.085c-24.581-39.774-14.34-61.243-39.957-91.247
  c-21.326-24.978-47.502-25.803-77.339-17.365c-23.461,6.634-39.234-7.117-52.98-31.273C318.42,87.525,265.838,64.927,210.333,65.331
  z M445.731,203.01c6.12,0,11.112,4.919,11.112,11.038c0,6.119-4.994,11.111-11.112,11.111s-11.038-4.994-11.038-11.111
  C434.693,207.929,439.613,203.01,445.731,203.01z"/>
<filter id="pictureFilter" >
  <feGaussianBlur stdDeviation="15" />
</filter>
</svg>

ok,

I did some debugging into TinyMCE and the problem seems to be that the svg element is detected as being empty and therefor removed. Unfortunatley there is no config way to change this behavior but there are some workarounds. 

1. Always have a name attibute for the svg element: <svg name="something"
2. Always have a data-mce attribute for the svg element: <svg data-mce-something="something"
3. Include some text content within the svg element: <svg>&nbsp;</svg>

Using these techniques i could succesfully store inline svg in an xhtml property

/Erik

Ah, that was the problem :) Thanks a lot!