Why does mailmerge change formatting?

[Baffled]

I created an excel spreadsheet, straight formatting, same formatting
throughout. When I merge into a Word document, some (not all) mailmerge
fields go bold mid stream. For example, 123 Main Street would end up as 123
(regular formatting) and Main Street would be bold. The Word document
doesn't show bold as being hidden within the line and the excel doesn't show
bold as being selected half way through the cell. Where does the bold
feature come from? I don't think it's a field switch since I could use the
same mergefield (<1>) in 100 places and the error pops up in say 10. I even
tried to copy the field where it showed correctly, but once merged, the error
reappeared as if I never changed it. Anyone have any ideas?

 

[Peter Jamieson]

I can't say I have always fully understood what Word does, but does your
field have a \*mergeformat switch? and if so, does the behaviour change if
you remove it?

Peter Jamieson