The Canaries had built up a 3-1 lead at the Madejski after a blitz of four goals in 16 minutes before Holt was shown a straight red card in the final minute of the first half for a challenge on former Leeds left-back Ian Harte.
Holt - who had already netted - was late as he closed down Harte but his challenge was not high or reckless and manager Paul Lambert has every right to be aggrieved.
Lambert was later sent to the stands and instead it was counterpart Brian McDermott who saw his side come close to taking the win after a great second 45 minutes which should serve as a lesson of how to play against 10 men.
Holt had already threatened when the visitors went ahead through an excellent finish from Russell Martin in the 16th minute.
The former Wycombe defender combined well with Korey Smith on the right and found himself running onto the ball inside the area.
Captain Holt was square and looked the obvious pass but instead Martin clipped in a side-footed strike which flew past Adam Federici and kissed the underside of the crossbar on its way into the net.
Simon Church angled a difficult header onto the roof of the net as the hosts looked to react but instead Holt who doubled the Canaries lead with an opportunist strike in the 26th minute.
Chris Martin was muscled off the ball by Matt Mills near the touchline and the Royals captain looked to feed the ball back to Federici. However he failed to see the lurking figure of Holt, who easily intercepted the errant pass, rounded the goalkeeper and found the net from an acute angle.
It was a great finish from Holt - his sixth of the season - but to Reading's credit their heads did not drop and they found a goal just three minutes later.
Brian Howard's corner was met at the near post by Noel Hunt and while David Fox did well to smuggle the ball off the line, it fell to Harte's feet just four yards out and he swept home.
Norwich regained their two-goal lead in the 32nd minute. Chris Martin was fouled by Howard 25 yards from goal and stepped up himself to bend a powerful set-piece over the wall and into the corner via Federici's fingertips.
The chances were non-stop at both ends before Holt saw red. The captain was enthusiastic in closing down Harte - who had taken a bad touch - but his challenge appeared late rather than dangerous.
However referee Michael Oliver was in no doubt and produced a straight red card.
The hosts needed to strike early and make their extra man count in the second period and came desperately close to a stunning strike in the 50th minute.
Church picked up the ball 25 yards from goal and drove in a powerful effort which John Ruddy did brilliantly to tip onto the post.
McDermott introduced another attacking player in substitute Michail Antonio and his side were soon level after two goals in three minutes.
First Hunt chipped over Ruddy from a tight angle in the 59th minute from Jem Karacan's pass and then Hunt found Long inside the area moments after the re-start.
The forward toed the ball away from the sliding challenge of Simon Lappin and Oliver awarded the penalty.
Again it looked like Norwich might have cause for complaint as Long made no mistake to hammer in the equaliser.
Norwich were having to face tide after tide of attacks and Hunt should have headed the hosts in front from Harte's cross but could not keep the ball down.
Long was then denied by the legs of Ruddy as Reading pushed for the winner but despite a flurry of shots over the top eventually both sides had to be content with a point.
There was just time for Oliver to send Lambert to the stands after he ventured down the touchline to remonstrate with the official.