I want to change the icon that appears in the comment message, but I can not or did not do well.

I have these two elements. When I disable the line "content:  903" I can see default icon from Outsystems.

My icon is from an external library called icomoon, that transform svg in icons. I just only changed in the theme the line corresponding to this style, but it doesn't work

If you could help me, I appreciated.