I think it's a difference between European English and American English. American English would spell it "combating". Which I kinda learned was wrong in an Amer

I think it's a difference between European English and American English. American English would spell it "combating". Which I kinda learned was wrong in an American school. "Swimming", "running", "batting" come from "swim", "run", and "bat", respectively. The present participle form doubles the consonant at the end of the word "as a rule" I was told. A single consonant would mean that there is a silent "e" at the end of the word which suggests a preceding long vowel (e.g., cure -> curing, compete -> competing, combate -> combating). Anyway, it's because nobody follows rules when writing and speaking English and as long as the other person understood your meaning, your grammar was correct.