"Good for David but there goes another one I really like," replied another Twitter user.
Others tweeted of their "huge respect" for Shearer, with one calling him "the last moderately electable Labour MP".
"Such a loss to New Zealand politics," one person tweeted.
Sentiments were similarly positive on Facebook, and many on the Herald's page said Shearer would be a good fit for the job.
"David Shearer's background was with the UN and aid before he became a politician," wrote one woman.
"He is very much admired in the field so effectively he's returning to his specialist job. I wish him well."
Said another: "His experience makes it the right choice and his humanity makes him the best choice. He was and is too nice for politics."
Shearer, a former New Zealand Herald New Zealander of the Year because of his aid work, has previously worked for the UN in conflict zones including Rwanda, Somalia, Iraq, Afghanistan, Kosovo, Lebanon and Liberia.
On a Mt Albert community Facebook page, councillor Cathy Casey shared the news Shearer was stepping down.
Comments below her post congratulated Shearer, calling his recommendation "well deserved".
However some saw the resignation as another nail in the coffin for Labour, with one person saying the party would be "depleted" following Shearer's absence.
Another commented on the Herald's Facebook page speculating leader Andrew Little was the real reason for Shearer leaving.
"How many labour mp's have quit since the Little mouth piece has taken over, [sic]" the man wrote..
On Twitter a few digs were taken at Labour too, with one person joking Shearer might be looking for somewhere stable to work after seven years in the party.
"[H]e's found that in South Sudan."
The three-year civil war in South Sudan has forced more than two million people to flee their homes.
The UN human rights commission last week said ethnic cleansing was taking place and the stage was being set for a repeat of what happened in Rwanda in 1994, when 800,000 mainly Tutsis were killed in three months.
Shearer was elected to Parliament in a byelection in 2009, replacing former Prime Minister Helen Clark, who is head of the United Nations Development Programme.
He became Labour Party leader in 2011, after Phil Goff's election defeat, but resigned before a scheduled no-confidence motion by the caucus and was replaced by David Cunliffe.
There was concern at polling under Shearer, which was about mid 30s, but it has never bettered that since and is now in the late 20s.
A byelection in Mt Albert will be the second for Labour to defend, following last weekend's success in keeping Mt Roskill. Shearer won Mt Albert in 2014 with a 10,656 majority.
