Its one of webnovels new plans. They'll show off those with too much money on hand (though I still think the majority of multi 10 k coin givers are bots) in hopes that we will wonder if the books are just that good.
And its not entirely wrong, almost checked out Letters to Romeo earlier today just to see what the hell warranted gifts from one person in excess of 40k coins. 346 chapters with privledge and I was like nope, definitely a freaking bot.
Sadly much like the recommended reading added to our libraries there's no way to disable this spam until webnovel gets bored of it themselves.