This one drives me crazy. If anyone can shed light on the usage of conjunctive adverbs it would be appreciated. Spell check programs are quick to point out that you need a semi-colon prior to and a comma after the word 'however' (between two independent clauses that is) to avoid a fragment or comma splice. However (no pun intended), after the word 'therefore' I rarely see the comma even though it's presented in the exact same way. I have seen this in many types of scholarly writings and must assume that there is a special rule with 'however' that does not apply to other conjunctive adverbs.
Thanks much for any help.
Here are some correct sentences:
You wouldn't use a comma after this example, however much the grammar checker told you to. It is therefore not necessary.
However, in a sentence like this, it is necessary. Therefore, there are different contexts in which these words appear.