If I have a player dead to rights trolling on replay but namedrop him, will Riot take no action?

That's the way Riot handles it, but it's not how it SHOULD be handled. If you go to court, you don't leave not knowing if the other person was convicted or if they're walking the streets unpunished for their crimes.

I've had spans of multiple weeks where one to four of my teammates trolled every game. Didn't matter time of day/night that I played. Didn't matter if I swapped roles with people to give them their preferred role. Didn't matter if I was nice or mean or if I went out of my way far beyond what's expected to help them out; they just inted until the game was literally unwinnable - off laning phase alone. Then they continued to int. In scenarios like that, when 90% of your matches for 2+ weeks are auto-losses off the back of one or more teammates deciding to guarantee your team will lose before laning phase even ends it would really be helpful to know if any of said players were punished as they deserve to be. Not being informed of any of that and running into more and more of it every day (2+ weeks of it in 90% of games) leaves you convinced that nothing is being done to address the issue of inting. Which can lead to toxicity against teammates due to built up frustration at all the inting, any harassment/toxicity said people do to you, and lack of consequences for said inting players.

Giving feedback and actually punishing players who are truly inting (kda doesn't guarantee a player is inting or not; good kda can still int, bad kda might not be inting) would do much to reduce toxicity in the game. Which sounds like a pretty good reason to me for confirming if someone was punished or not. Knowing that such poor teammates are being removed from the game or forced to re-think and reform their actions would reduce stress and frustration that many players feel build up and explode when they end up dealing with several games/days in a row of intentional feeders. Sounds worthwhile to me.

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Shitty automated reply, usually. You have to deal with not knowing if the troll ever met justice because Riot doesn't think that closure means anything.

This.

I have never issued a support ticket that was not answered within a few days by an actual person.