Nope. When you say it doesn't work, what exactly happens?
This is how the string file works:
Each string entry has 3 lines: StringInfo, ID, and Value. The "stringInfo" tag tells the game to expect an ID and Value to follow. The ID is the internal tag for the string. The Value is the actual text displayed in game.
So if an entity contains this line: nameStringID "IDS_ABILITY_BEAMBLAST_NAME" the game is going to search through the stringInfos until it comes across the matching ID "IDS_ABILITY_BEAMBLAST_NAME", take its Value field, and display it in game.
So, when you make your ability, if you give it a nameStringID "IDS_ABILITY_MYSUPERABILITY_NAME" and a descStringID "IDS_ABILITY_MYSUPERABILITY_DESC", you will need to add this to the English.str file (anywhere works):
stringInfo
ID "IDS_ABILITY_MYSUPERABILITY_NAME"
Value "Super Ability"
stringInfo
ID "IDS_ABILITY_MYSUPERABILITY_DESC"
Value "This super ability does all sorts of mean things."
and then increase the string count number up top by 2.