We have complained to Duolingo staff about it. Other languages have also complained that it is a minor annoyance, though for us is a major annoyance. If you look carefully, there's a minor curl at the bottom of the l that is absent from the bottom of the I. It also gets easier to know which is which because Klingon spelling is pretty regular and your begin to get a feel for where there should be a consonant and where there should be a vowel. For instance two vowels never appear next to each other and all consonants should have at least one vowel on one side of the other (with some very rare exceptions that don't include L's). Hopefully one day Duolingo will decide to make a helpful change to three font, but until then look carefully for the curl.