and, FWIW, you can get formatted text by combining simple html markup with the textutil and pbcopy commands.
Code:
do shell script "echo " & quoted form of "<i>Hello</i> Mom!" & ¬
" | textutil -format html -convert rtf -stdin -stdout | pbcopy -Prefer rtf"
tell application id "com.omnigroup.omnifocus"
activate
tell application id "com.apple.systemevents"
keystroke "v" using {command down}
end tell
end tell