People trying to use US International keymaps aren't able to enter characters by combining dead keys such as î or õ unless this is working. The keymap for this to work exists but is not included in the build. :( This is issue #122 upstream and it was fixed by us back in July. The changes just haven't trickled down to ThinLinc yet.
This was included in one of the recent vendor drops of rdesktop and should be fixed now.
Verified using ThinLinc 4.8.0post build 5646, works as expected. Can specify and produce combinations of dead keys and i for example.