I'm not using EL in order to play with RetroArch, I'm using EL for MAME and for documentation and classification of my No-Intro roms as your frontend is much more interesting for these actions.
This is what you can find in their documentation:
The thumbnail file should exactly match the game's title as listed in the playlist with an important exception. The following characters in playlist titles must be replaced with _ in the corresponding thumbnail filename:
So every game with one of those characters are not diplayed in Emuloader. I'm using these snap packs as they are the most complete for No-Intro users.
But I agree you don't have to rewrite your frontend just because somebody else took another decision about naming. This is just a little inconvenience for me...