Okay so, these existed in the past, but were culled during the move to new-formats.
These of course would be purely a thematic thing, with no gameplay effect. They animate when a lemming walks past (presumably, both a "once" and a "infinite" version could exist), but otherwise do nothing.
The common argument against them is that if an object looks like it gets triggered when a lemming walks past, it should do something, and that it's misleading if it's not.
I'm not convinced by this. I do understand where it's coming from but, "nothing" is just another possibility to a list of things it could do. Without any context beyond "it animated when a lemming walked past", you don't know exactly what it does. You have to either look closer, or use CPM, to find out regardless - or, use context, like "what does the object look like?", at which point these are no different to anything else in regards to "don't make them look like things they aren't". (Even if you look at "did the lemming disappear?" - if it does, that could be a trap or a teleporter. If it doesn't, that could be an unlock button, a pickup skill, or a splitter that's pointing the direction the lemming is already facing.)
The benefit of course is purely an aesthetic one; but the effort to do this is relatively low - almost all the code could simply be copied from traps, with the "kill the lemming" lines removed.
One other reason is - some people have expressed interest in trying to do this anyway; one even trying to figure out a workaround to emulate this with features that do exist (it's possible - but I'm not going to explain how, and I don't believe that person figured it out). This may be a case where it's better to implement it properly, at which point CPM can hide or appropriately label it, or even potentially an option can be added user-side to hide them (or make them not function).
What's other people's thoughts here? Does anyone feel I'm underestimating how significant the "it should do something" factor is, or that there are other reasons against this?