This, as many other items which come up on the BB are IMO much ado about nothing (well almost).
I am surprised at the calvinists since they know nothing can frustrate the will/call of God.
"Altar call" in my book is a verbal metaphor for the following verse:
Matthew 11:28 Come unto me, all ye that labour and are heavy laden, and I will give you rest.
OK so the phrase might not be literally correct but at least metaphorically acceptable (imo) presuming of course that the metaphor points to the REALITY of the Blood Atonement of the "altar" of the cross. Hopefully the preacher has made that clear as someone pointed out (Hebrews 13:10).
Secondly and IMO, an "invitation" is valuble in that what do we know but that the Lord is dealing with an individual and has (humanly speaking) led him to your local church for food for his hungering and thirsting soul?
OK, so we should try to be correct considering what we are inviting the individual(s) to do.
In by-gone days the altar call/invitation was to a mourner's bench for those under conviction of sin or inquiry rooms to determine if the "religious" desire was from God or the flesh.
Personally I don't see a problem unless a church is prmarily interested with a head count and not the gathering and/or the feeding of the newly found sheep of His pasture.
Nonetheless, its a worthy debate because it seems some local churches have lost sight of the purpose of the "altar call" or "invitation" which no doubt has led to an abundance of tares in the kingdom of God.
HankD