"You will walk, Torg."
Here are some hints that may help you tell a capital i apart from a small L in Klingon, apart from the little curl at the bottom of the l (small L) that isn't at the bottom of the I (capital i).
Klingon is pretty strict on consonant and vowel clusters. You can't have two vowels in a row, and you can't have more than two consonants in a row (with three exceptions, none of which involve l, small L, in the middle).
Note that ch gh ng tlh count as single letters in Klingon, so you might have words such as chechtlhutlh (a kind of alcoholic drink) -- that only has two consonants in a row in the middle: a ch next to a tlh.
So every I (capital i) will be next to a consonant on the left and/or the right, and every l (small L) will be next to a vowel on the left and/or the right (or will be part of the spelling of the Klingon letter tlh).
It may also be helpful to know that there is no separate letter h in Klingon; it's only part of the spelling of the letters ch gh tlh.
So if you see tlh with small h, that's the single letter tlh (which has small L in the middle), while if you see tIH with capital H, that's a syllable which starts with the consonant t, has the vowel I (capital i) in the middle, and ends with the consonant H.
Note also that y w ' (wye, double-you, apostrophe) are all consonants in Klingon.
So in bIyIt, you can see that b - y - t are definitely consonants.
This means that the things in between have to be capital i's. You can't have bly with an L in the middle because that would be three consonants in a row, and you can't have ylt with an L in the middle because that would also be three consonants in a row. But you can't have three consonants in the row with the middle one being an l, small-L.
(If you're curious: the only cases where you can have three in a row are when the first two are either w' or y' or rgh*.)
It may also help to know that Klingon syllables (and also words) usually end in a consonant -- so if something looks like a | at the end of a word, it's probably a small-L rather than a capital-i.
The main exception for syllables ending in a vowel is verb prefixes such as bI- or jI- or Da-.
You might want to read the Tips, which can help to earn you of expected confusions such as this. Duolingo has hidden the Tips, so I want to make sure you know about them and where to find them.
If you are doing the course on iOS or Android, you cannot currently access the Tips through the app. To access the Tips, you will have to access the course using a web browser at https://www.duolingo.com/. You can still do it on your mobile device, but you will have to use the web browser instead of the app (or you can do it from a computer). When you click on a Skill, it will expand to reveal a Start button and a Tips button.
If you click on the Tips button it will reveal the Tips and give you a detailed explanation of the grammar that is introduced in that Skill. If you have questions after reading the Tips for any Skills, we are happy to answer your questions, but many of your questions will probably already be answered in the Tips.