The poster showed Gandhi with several heads, with the title "Bharat Khatre Mein Hai - A Congress party production. Directed by George Soros".
Despite being exempted from appearing in court, Rahul made showed up for the defamation case.
He said the Maha Vikas Aghadi alliance of three parties -- Sena-UBT, Congress and Nationalist Congress Party -- was formed to protect democracy and it was necessary to work unitedly for it.
However, speculation remained rife that the meeting was part of Banerjee's plan to form an opposition front with regional players minus the Congress.
Pronouncing the judgement, Justice Khanna said the court has rejected all the petitions, including those seeking resorting back to ballot papers in elections.
Congress chief Mallikarjun Kharge, general secretary Priyanka Gandhi Vadra, senior leaders K C Venugopal, P Chidambaram and Salman Khurshid were among the party's top brass taking part in the satyagraha at Rajghat.
Aakraman ho raha hai, maza aa raha hai, says Rahul Gandhi.
The central probe agency had on Friday carried out a fresh round of searches in connection with the case, they said.
Right to comment on content on social media or TV channels is a facet of free speech under the Constitution and it will be in the interest of the public that every broadcaster has the right of criticism and review even in relation to programmes created by others, the Delhi high court said on Friday.