Inexplicably the then world champion Anand played the dodgy triangular slav in the 2013 match against Carlsen, and Carlsen didn't try to refute the Marshall Gambit with 6Bd2.
Don't think any 1.d4 club player refuting the gambit anytime soon. Especially as most are not particularly at home in sharp positions.
Carlsens 6.Nc3!? was a nice psychological choice. Before the game was played most black players believed that 6...c5 is just an easy equalizer. As the game has shown, things are not that easy for black. (Black might still equalize but he needs to know some very precise moves.) Some GMs started playing 6....e5!? as answer to Sc3, but even here White might push for a slight edge. And obviously as a great theoretician Anand would be greatly prepared against the sharp lines with 6.Bd2. (Not to mention that this gambit isn´t really Magnus´ style of play.)
The last time I checked the Marshall gambit black seems to be alright objectively. But White has the choice between this slightly better endgame with 6.Nc3, some forced repetitions and some very dangerous lines, where the slightest slip might cost black the game. I guess this combination of options make the whole variation quiet unappealing for black players.
Every so often on this forum someone responds to one of my old threads as if it had been created just today and not five+ years ago.
I have made great strides as a chessplayer in that time but the quality of advice you can get on this forum, meanwhile, has stayed just the same 
Every so often on this forum someone responds to one of my old threads as if it had been created just today and not five+ years ago.
I have made great strides as a chessplayer in that time but the quality of advice you can get on this forum, meanwhile, has stayed just the same
yes I have petitioned many times for chess.com to lock old threads as it is incredibly annoying and part of what makes these forums not so good.
Every so often on this forum someone responds to one of my old threads as if it had been created just today and not five+ years ago.
I have made great strides as a chessplayer in that time but the quality of advice you can get on this forum, meanwhile, has stayed just the same
yes, excellent advice!
In the Martinovic game--White should never have agreed to a draw.
c6-d5-e6 is the "triangular" Slav - it's not very good and is rare among the top players.
According to the lichess database it's not the Marshall Gambit until Bd2. White can bring the knight back to c3 and still be ahead or he can go Bd2. Check the statistics among strong players - 56% win rate, check the computer, +0.4. e4 actually has the best results of any of the moves among top players.
According to the lichess database 3. ... Nf6 is 21 times more common than e6 or the triangular slav). What does Nf6 prevent? The only move it prevents is e4, if you play e3 then they can just play Nf6 on the next move and will have escaped. It's black who is playing a dodgy line, not white. White is absolutely correct, the question is how to "refute" the triangular Slav.
The only reason I can think of why e4 isn't the most common continuation for white is because they're afraid of being caught up by tricky black preparation.
A quick filtering over a current database reveals more than 570 games played between players rated over 2400 (both of them) in the last 5 years, and with blitz & rapid games excluded.
Verdict?
(1) You have no idea what you are talking about,
(2) I was just wasting my time, as I knew (1) already.
570 out of how many that were in that position?
The main lichess database only has 2200+ rated OTB games from 1952 to 2019.
21 times as much like I said.
Verdict?
1) You were unaware this opening was a sideline at least until recently.
2) You always waste your time by coming here anyway.
c6-d5-e6 is the "triangular" Slav - it's not very good and is rare among the top players.
According to the lichess database it's not the Marshall Gambit until Bd2. White can bring the knight back to c3 and still be ahead or he can go Bd2. Check the statistics among strong players - 56% win rate, check the computer, +0.4. e4 actually has the best results of any of the moves among top players.
According to the lichess database 3. ... Nf6 is 21 times more common than e6 or the triangular slav). What does Nf6 prevent? The only move it prevents is e4, if you play e3 then they can just play Nf6 on the next move and will have escaped. It's black who is playing a dodgy line, not white. White is absolutely correct, the question is how to "refute" the triangular Slav.
The only reason I can think of why e4 isn't the most common continuation for white is because they're afraid of being caught up by tricky black preparation.