I'd say that when terms are used that don't generally correspond to how most of the internet web forums use terms, it's probably not the best idea to assume that these terms actually mean anything to users who don't already know the terminology. Similar to how on User Settings, I am pretty sure I saw those depth things faintly earlier, but since they referred to 'Notes', not 'posts' or 'threads', I really didn't know what they were referring to at all, and it was only after I got the hint to look for 'depth' that I realized those must be referring to the depth of the thread postings. The term 'depth' is not one I recall ever seeing in this context before, but usually these things aren't hidden by default, they are on by default, so maybe it was something I'd simply never run across. Basic usability rules: if you need to know what the stuff you are looking for is before you know what it is, that's not great.

There are now that I think of it a few tech sites that use this hidden by default method, but I honestly find them so annoying that I just ignore them, so I guess if you were used to those, this might make some sense. Generally my view on forums is if I have to join as a member to make the site usable, then I will generally just skip it and go somewhere else. Perlmonks is somewhat special because it's such a great resource, but the interface could use some work, it doesn't do Perl justice imo.

These things could be resolved by adding a few simple words to connect the dots, however, no worries, it was a one time thing, though I had to actually really think about it to figure out what these terms actually referred to. It's very easy to know what stuff means then comment that it said it right there, the problem is, it's not actually as obvious as you might think, I've never seen this type of terminology used on internet forums before, and I've used a ton of them, way too many, sigh. So I would hesitate before believing something is as obvious as you might believe it to be.