Titillium Web is the font used for the text in the profile information to the left of each thread post, and each thread title in the forum index. At the size that it is, the lower-case I and L characters are identical. The following CSS fixes the issue;
font-size: 16
Additionally, as you can see, text in code blocks is illegible because it’s light-on-light. Changing that CSS to the following alleviates that issue and allows code blocks to be in-line;
display: inline-block;
color: #1d1f2a;
margin: 0;
padding: 0 5px;
font-size: 80%;
margin-bottom: -5px;