I'm not sure if there is an established/recommended way to avoid copy/pasting in UML Communication Diagrams. Probably there isn't because of this paragraph in UML 2.5 Beta 2 specification:
Source: http://www.omg.org/spec/UML/2.5/Beta2/PDF
17.9 Communication Diagrams
...Communication Diagrams correspond to simple Sequence Diagrams that use none of the structuring mechanisms such as InteractionUses and CombinedFragments...
In UML Sequence Diagrams you can use fragment with ref operator (interaction use
) to indicate that another diagram should be "pasted" here.
Considering this example sequence diagram:

corresponding Communication Diagram might look like this:

Note that in the above diagram:
- message
0.4
represents simplified message flow. Details of the Send Report
interaction are not shown
- messages
0.2
and 0.3
contain guard expressions
which are used to represent if
branching
More readable representation of complex if
branches can be achieved by using the decision node notation as shown in the UML Interaction Overview Diagram below:

Note that the above diagram uses inlined "pasted" interaction Send Report
. Instead of showing the interaction details you can use simple interaction use
notation same as in the first diagram above.
Disclaimer: the diagrams are not perfect and may be they are not even correct. Use at your own risk