Is coute correct (3rd pers. sing., pres. indic. act.)? It is given as correct along with coûte .
jcjenks advice is sound.
In fact, the accent circonflexe was removed from this word in the French spelling reform of 1990. This must be why Duolingo accepts it.
I don't know how the other spelling reforms have caught on, but this one is definitely not popular. I know teachers didn't like being told not to mark "coute" as incorrect.
Information about the reforms here: http://www.orthographe-recommandee.info/regles4.htm.
(@Sitesurf. Yes, accents can be clues about the etymology of a word and can often help anglophones see cognates. I think, however, that keeping them just for that is daft. This is not something I would say in French company just yet... )
I like accents where they help with pronunciation. The é is my friend, and as fast to type on a QWERTY keyboard as on an AZERTY, that is Alt Gr followed by e for é, or E for É.
The reforms are not totally dead. When someone in her early 20s proofread a form for me, just two weeks ago, she pointed out that my spelling of "porte-monnaie" was old-fashioned. The new alternative spelling was not in the 2009 dictionary I use. Young people seem to use the dashes-between-digits for numbers.
Some years ago there was a survey about the effect of the reforms. One of the questions was about "coute" and the percentage of French people who knew about it was 3.3%. None knew about the suggested change of "oignon" to "ognon".
Edit: Found reference to 2002-2003 survey. .Modified paragraph above slightly. http://fr.wikipedia.org/wiki/Rectifications_orthographiques_du_fran%C3%A7ais_en_1990#Diffusion
Thanks, jcjenks and Mizotte. V. interesting. duolingo does not consistently require forms w/ and w/o the circumflex in this person of the pres. indic., as it did in this case. Very VERY interesting that there was a spelling reform. I'd never heard of it. Thanks much for the reference.
You're right Mizotte, the French love reforms only not to respect them. However, I have never heard of removing accents circonflexes, more about funny things like 'nénufar' instead of 'nénuphar... (waterlily). The 'accent circonflexe' on the 'u' in 'coûte' comes from a contraction of 'couste' in old French (sounds more like 'cost', doesn't it?). Same story with 'bâtir' (build), 'tête' (head) or 'hôtel'.