Seems like a Solution

Here's the question that I just submitted to the Support team:

In the 'Long Move Timer' section of https://support.chess.com/en/articles/8593801-how-does-game-abandonment-work it states that "After 10 moves, you can use as much time as you like on any move." That rule is being terribly abused by some poor sports. As an example ...
We both had excellent connections (4 bars) in my latest 30-minute Rapid game. At one point my opponent had a significant material advantage (+8) but after 37 moves I had turned the tables and had a slight lead. That's when they stopped playing. I waited +15 minutes before a countdown timer finally showed up with only 4 minutes left on their clock. Seconds after that countdown appeared it vanished and I had to wait out the rest of their time.
Players should be allowed reasonable time to calculate their moves. I do not dispute that. But what's reasonable? A 30-minute Rapid game shouldn't be treated the same as a 14 days match.
Why not allow players to stipulate the allowable move time using the Custom feature the same way that we can stipulate the game time? Seems like a workable solution.

I'll let you know what response I get.

And here it is, with non-relevant parts omitted ...

Thank you very much for your response and for all the information, including the link of the game, all this evidence really help us!

Firstly I would like to let you know that we don't allow Stalling on Chess.com.

So I've already compiled a report about this user susssssssssss987 so he will receive a sanction for this.

In addition to this I'll send this case to the developers so they can analyze the abandonment rules se we can include this kind of cases there. Thank you very much for bringing this up to us and for your help to improve Chess.com!

Hopefully the developers will do something meaningful because it happens a lot and it's extremely annoying.