Even if hardware support existed, it seems like a variable length encoding has some inherent overhead relative to a fixed length encoding. If you have a "base length" of e.g. 32 bits and occasionally expand to 64, there's an inherent cost there in both computation and memory, presumably for greater precision. Perhaps that overhead could be minimal with hardware support, but it seems it must have some.
Those are type one unums, not posits. What you are saying about variable length encoding may be true, but it does not actually apply to the current comparison. Type 2 unums are also fixed length, but have other issues.
In my defense, the comment he replied to got downvoted and I thought it was nestorD, so I was "primed" to misinterpret his comment as criticizing unums in general.
