In both cases, it reads to me as if the first instance (he said definitely/clearly) is a description of HOW he said it. The second instance (he definitely/clearly said) reads as if I, the narrator, am certain that this was what he said. Here, I don't see the need for the comma in the first example, unless you're using it to put the adverb on some sort of pedestal, to spell out how sneaky she is. In both examples, it's a matter - as has been said by others - of what sounds right.
I know I'm late in replying, but I disagree. There are more than enough words to replace "said" if you don't want to use an adverb. http://www.spwickstrom.com/said.pdf
I think you might have picked me up wrongly. I actually totally agree with you. Here is what that particular paragraph I wrote actually said: I was arguing against the notion that you should never use adverbs in dialogue. I did finish up with:
The problem isn't that you should never use an adverb or something besides 'said'. The problem comes from not using them selectively. For example we often try not to repeat the same word in a passage. But once in a while one repeats the same word several times for an effect. Some less experienced writers try to do that with 'said' and in doing so take a similar list of words one can use instead of 'said' and try to eliminate using said either altogether or to minimize using it repetitively. And it's stronger to use the whole passage to impart the emotion, rather than a version of said or an adverb. That doesn't mean never use any adverbs and always use said. So the admonition to not use adverbs and to use said, like a lot of writers' admonitions, is meant to address a common mistake made by new writers.
Then came forth Steerpike from on high, and said, "Useth thou not weak verb/adverb combinations, but instead useth thou strong verbs, that thy reader might love thee."
Interesting, I thought that using adverbs after dialogue was considered to be a "Swifty", but I see now that that's only if you create a pun in the process. "My bottom hurts," Tom said cheekily. I still try to avoid adverbs whenever possible, but to each their own.
I do my best to avoid adverbs altogether. Imply the sneakiness with action (or come right out and show it) then write the dialogue. Or do it the other way around. If it were any other verb besides 'said,' I'd say find a stronger verb. But we're told that 'said' and 'asked' are practically invisible (and I think that's mostly true [and how does one say 'mostly true' without an adverb?]) so we're kind of stuck with it. Which is why, in cases like this, I do my best to imply/show the crap out of that sneaky without resorting to adverbage.
"Mostly true" is a good point. I think that it's much more...acceptable? to use adverbs to modify adjectives than to use them to modify verbs. If you're modifying an adjective, it's probably the most natural way to do it and won't stand out too much, but with a verb, well, like they always say, find a better one.