LifeDeath wrote:When I considered it, I thought mainly of adjectives that people use to describe the way an action is being done.
It can be their estimation, like characteristics:
"He's doing it in a weird way" or "He's doing it weirdly". Other pairs are possible, such as "strange/strangely, odd/oddly, reluctant/reluctantly" and so on.
"He's doing it in a reluctant way" sounds odd. You can be reluctant to do something, but there's not really a en established way of doing something that could be characterised as "reluctant".
LifeDeath wrote:It can also be an obvious objective evaluation about an action:
"He's doing it in a slow way" or "He's doing it slowly". Other pairs are possible, too: "loud/loudly, quick/quickly, accurate/accurately" and so on.
In all of these cases, the adverb is vastly more common than the paraphrase. Like I only found 94,000 Ghits for "in a slow way" and many of these are from dictionary definitions for "slowly".