Source: Per news clipping post by David Archer at 18th Battalion Facebook Page (not group).
Find-A-Grave
This man was assigned otthe 18th Battalion on 6 September 1917 and was on the roll of the Canadian Corp Reinforcement Camp (CCRC)” on 2 February 1918. He in noted to rejoining the CCRC on 12 February 1918 and then was transferred to the CCRC on 18 August 1918. He served with the CCRC until he was transferred to England with B Wing Canadian Concentration Camp.Though he shows that he served with the 18th Battalion he never joined the Battalion in the field. This camp was located initially at Lilliers and then was moved to Aubin St. Vaast in June 1918.I checked the war diary of the CCRC and it was at this location from that date until it was shutdown in 1919. Was the CCRC camp near the location of this graffiti?
War Diary of the 18th Battalion CEF 