Sheikh Assim Alhakeem answers a question about hadith instructing to not sit leaning on the left palm. Ima instructs that leaning on both palms is permissible.
Some of the scholars described this manner of sitting as makrooh. Abu Dawood included this hadith in his Sunan (12/480) in a chapter entitled: Chapter on disliked manners of sitting.
Ibn Muflih (may Allah have mercy on him) said:
It is makrooh for anyone to lean on his left hand, placing it behind his back.
End quote. Al-Adaab ash-Shar‘iyyah (3/288)
Something similar was also stated by as-Safaareeni in Ghidha’ al-Albaab (6/76)
Shaykh ‘Abd al-Muhsin al-‘Abbaad said:
It may be that what is meant by makrooh here is that it is haraam, or it may mean that it is disliked. But the fact that in this hadith this manner of sitting is described as the manner of sitting of those with whom Allah is angry indicates that it is haraam. End quote.
Sharh Sunan Abi Dawood (28/49)
To sum up:
It is not allowed to sit in this manner in prayer or otherwise, regardless of whether or not the intention is to imitate those with whom Allah is angry of the Jews and other arrogant people. The fact that this manner of sitting is described as the manner of sitting of those with whom Allah is angry and of those who are punished indicates that the view that it is haraam is stronger than the view that it is makrooh.
And Allah knows best.