Summary:

A user creates a new email template for opportunities that includes the following merge fields:

Description: #oppo_description#
ID: #oppo_opportunityid#

Symptoms:

When this template is used on an opportunity the following results are displayed:

Description: Training solution for 40 users                   
ID: Training solution for 40 users  

What you would expect here is for the ID field (#oppo_opportunityid#) to be populated with the ID but it is populated with the product description on both lines.

Resolution:

The resolution to this is to navigate to the view vSummaryOpportunity and add in the following to the view (highlighted in yellow below):

CREATE VIEW vSummaryOpportunity AS SELECT epd_pers.epd_EmailAddress as Pers_EmailAddress, epd_pers.epd_PhoneCountryCode as Pers_PhoneCountryCode, epd_pers.epd_PhoneAreaCode as Pers_PhoneAreaCode, epd_pers.epd_PhoneNumber as Pers_PhoneNumber, epd_pers.epd_FaxCountryCode as Pers_FaxCountryCode, epd_pers.epd_FaxAreaCode as Pers_FaxAreaCode, epd_pers.epd_FaxNumber as Pers_FaxNumber, epd_comp.epd_EmailAddress as Comp_EmailAddress, epd_comp.epd_PhoneCountryCode as Comp_PhoneCountryCode, epd_comp.epd_PhoneAreaCode as Comp_PhoneAreaCode, epd_comp.epd_PhoneNumber as Comp_PhoneNumber, epd_comp.epd_FaxCountryCode as Comp_FaxCountryCode, epd_comp.epd_FaxAreaCode as Comp_FaxAreaCode, epd_comp.epd_FaxNumber as Comp_FaxNumber, Person.*, Company.*, Opportunity.*, Account.*, oppo_opportunityid AS oppo_oppoid  FROM Opportunity LEFT JOIN Person ON Oppo_PrimaryPersonId = Pers_PersonId LEFT JOIN CRMEmailPhoneData epd_pers ON epd_pers.epd_EntityID = 13 AND epd_pers.epd_RecordID = Pers_PersonID LEFT JOIN Company ON  Oppo_PrimaryCompanyId  = Comp_CompanyId  AND Comp_Deleted IS NULL LEFT JOIN CRMEmailPhoneData epd_comp ON epd_comp.epd_EntityID = 5 AND epd_comp.epd_RecordID = Comp_CompanyID LEFT JOIN Account ON Oppo_PrimaryAccountId = Acc_AccountId WHERE Oppo_Deleted IS NULL

Once this is updated perform a metadata refresh.

Then perform the merge again it will now show the fields correctly.

e.g.
Description: Training solution for 40 users                   
ID: 19