Danson was knocked out cold after being caught in the middle of some punching tackles exchanged between Palace's Michael Hughes and Albion's Johnson. The official came off worse as heads clashed and seven minutes of treatment were needed before the game restarted.
An uneventful first half saw few opportunities although Jason Koumas struck the foot of the post in the 30th minute for Albion.
Straight after the break, Dougie Freedman forced Russell Hoult into making his first save but it was the visitors who went in front in the 51st minute.
It seemed a nothing lob from Alassane N'Dour but it proved to be enough to drop over the Palace defence and Rob Hulse raced on and fired past Cedric Berthelin.
The Eagles had to wait just eight minutes for Freedman to make it all square with a simple tap in after good work from Johnson.
Then Koumas fired a tremendous 35-yard free kick which flew past the Palace wall and into the corner of the net. But three minutes into injury time Johnson levelled for Palace after Hoult failed to hold Shaun Derry's 20-yard shot.
Palace manager Steve Kember said after the game: "I think we played them off the park in the first 35 minutes and yet again we didn't get what we deserved."