Some accent mistakes cause "incorrect answer"
Usually, Duolingo (in Spanish) lets you slide on incorrect accents, like "¿Que estas haciendo?" (should be "¿Qué estás haciendo?").
However, sometimes my timing is a bit off, and I place the accent on a letter that shouldn't be accented in Spanish. For example, instead of "sábado," I might write "śabado." Clearly, this is incorrect, but it seems like it should be allowed to slide just like the above errors—even more so, in my opinion, because it's far less likely that you think this is the actual correct answer than that you made a typo.
My keyboard allows me to type any of the following accented characters:
áćéǵíḱĺḿńóṕŕśúǘẃýź. These are Unicode codepoints
225, 263, 233, 501, 237, 7729, 314, 7743, 324, 243, 7765, 341, 347, 250, 472, 7811, 253, 378 in decimal, or
0xe1, 0x107, 0xe9, 0x1f5, 0xed, 0x1e31, 0x13a, 0x1e3f, 0x144, 0xf3, 0x1e55, 0x155, 0x15b, 0xfa, 0x1d8, 0x1e83, 0xfd, 0x17a in hex.