Obviously removing the free coin just for playing solves the issue, but ruins it for other people.
Easy solution would be enhanced prizes for the top 4, rather than only the top 1. Lag alone makes #1 impossible for some people, which tempts them to also AFK bot.
Slightly more involved method is to attack the method used to farm: Autoclickers.
Right now, you have to click 2 spots to start a match, so this stops simply using a turbo-fire mouse to cheat.
To improve "protection" you can make us click an "Are you sure?" button after we choose to use Solo/Team/Guild. But make the "Yes" and "No" (back to type select) and "Cancel" (back to character control) randomly choose which side of the confirmation to appear on.
This makes the farmers need to spam click, as 66% of the time they won't start a game.
Now you also make the "Fill it up!" and "Add 1" buttons appear in the same space that the "Yes", "No", and "Cancel" buttons had appeared.
This makes it so that a spam clicker will pay tribute to Krogmo for the rest of us. The farmers can avoid this by clicking slowly, but with the first change made, that means fewer games farmed for them, ideally to the point of making the farming not worthwhile.
You could also remove the automatic exit from the final scoreboard after 5 minutes. Require that we click a button to exit, and preferably make it overlap the space used for the button to cancel waiting for a match to start. Then when the farming bots click in hopes of leaving a room, they may instead cancel waiting for one.
These simple changes to button layout will have nearly no impact on people actually playing the game, but increase the complexity of setting up a farming bot well beyond the current level, hopefully cutting the total AFKers down by far more than 50%
click a button that appears
on a random spot on the screen
to confirm that you want to revive.....
also good for ppl who like to choose the moment of revival
(but not the location, i.e you still respawn to a random spot)
so how this works is that
if you do not revive, you do not earn points.
then
set a threshold of points required to be eligible to earn coins.
of course, ppl can spawn and wait to die, but at least you waste their time doing it.
i got this idea reading TS post, fyi