#Trending: Arabs react to the release of al-Jazeera journalist
Mansour was freed from custody in Germany without charge on Monday, and has since arrived home in Doha, where the Qatari satellite network is based.
Mansour had been held by German police since Saturday, after an Egyptian arrest warrant accused him of committing "several crimes".
Social media has been torn between his supporters and those who questioned his integrity. At several points, he was called a "traitor".
@MusaadAlSenani Ahmad Mansour has betrayed his country several times for his extremist support of the Muslim Brotherhood. Justice will be served someday and he will be held. Egypt’s rights will not be lost.
Mansour received widespread support from journalists and human rights activists, as well as from well-known Islamic scholars and figures.
Yusuf Qaradawi, chairman of the International Union of Muslim Scholars, tweeted: "Free countries constantly try to protect their citizens' freedoms at all costs. Autocracies prosecute their citizens unfairly, inside and outside their borders."
The Kuwaiti leader of the country's Muslim Brotherhood branch also congratulated Mansour on his release.
@TareqAlSuwaidan: I send my congratulations to my brother and media figure Ahmad Mansour for defeating the evil of the coup supporters, and getting released free of charges.
Others simply resorted to sarcasm, comparing Germany's judicial system to its Egyptian counterpart.
@AlaaAswany: After the release of Ahmad Mansour, we can now be sure that the German judiciary is politicised and follows the orders of security authorities. Our hearts go out to the German people, who are deprived of the blessing of the glorious Egyptian judiciary.