Complex sentence: A conjunctive adverb and a comma (or a conjunctive adverb between two commas) is not strong enough to separate two independent clauses and creates a comma splice; only semicolons and periods are strong enough to separate two independent clauses without a conjunction.
Split into simpler sentences: A conjunctive adverb and a comma (or a conjunctive adverb between two commas) is not strong enough to separate two independent clauses and creates a comma splice. Only semicolons and periods are strong enough to separate two independent clauses without a conjunction.