As a deacon (through one of the several routes to the diaconate) I'll hold comments as I have a bit more curiosity than opinion. I became a member of the ELCA shortly before the merger. In fact, a number of deacons in NY in the AELC were rostered as AIMs in order for to stay on the roster with the merger. In the AELC the deacon was accepted. In the LCA not quite as well. May I ask someone with both backgrounds why and why not? I've no idea where other denominations such as ALC fell on this issue. Thank you!
Well, that's really the root of the problem, or one of them. Both the meaning of the office and the terminology used was different in different church bodies. As far as I can recall, the ALC didn't really have the office of deacon as a form of ministry recognized by the wider church; "deacon" was a term used in some congregations to designate a variety of different local functions. I'm not sure about the LCA or the AELC--though it was the AELC that caused problems in the merger process because of their "minister" status for parochial school teachers. The merger commission ended up punting, acknowledging that they had no consensus and recommending that the new church set up a committee to study the matter.
The ELCA task force in 1991 proposed three options: (1) Three-fold ordained ministry of bishops, pastors and deacons; (2) Two-fold ministry of "Word & Sacrament" and "Word and Service" with only the former being "ordained" (the others being "lay ministry"); (3) Single office of ordained ministry (which was essentially the status quo).
The response from the church generally favored option 3, though the bishops favored option 2. The task force ended up recommending option 2, but with "Word and Service" ministers also being ordained. But then the Division for Ministry offered a different tweak: a single ordination rite for all, but then different "installations" for bishops, pastors, diaconal ministers. The churchwide assembly didn't quite buy that, and what came out was essentially a two-fold ministry: ordination to word and sacrament ministry, and a roster of lay ministers who were not ordained (but had various educational requirements, etc.)--and of course this meant keeping the plethora of different "lay ministries" pretty much intact.
In a nutshell, there were a cluster of issues going on here, of which the terminology of the office was only one. Really in my view the "dividing line" was between those who saw deacons (and associates in ministry, and deaconesses, and diaconal ministers) as "ordained ministers" or as "lay professional ministers." There were multiple side issues--what to call those in this office, how to enter them into this office, how to treat them when it comes to the Almighty Representational Principle, etc.