I think its superfluous. 

It all depends on how the meaning of “appendix” is perceived: if, even without the now-removed stipulation, appendices are taken to be a mere explanatory adjunct, then the wide-ranging function of this particular appendix isn’t immediately apparent in the Ruleset’s introduction, and the term in itself is not as self-explanatory as it might initially seem. (That wouldn’t be a problem for people familiar with the Ruleset, but then again, they’re not the target of the sentence in question.)

If, on the other hand, we agree that appendices may ordinarily perform the function that this one does, then no additional explanation is needed.

Seems useful.

Would recommend quoting the text you’re replacing, if a proposal is simple enough for that to still be readable: it saves voters from having to open another tab to see what you’re actually changing, pre-empts unnecessary “this is great except I don’t like X” vote negotiation (where X was already part of the original rule) and - perhaps most importantly - gives a safety valve against accidentally overwriting the wrong paragraph, if you miscounted and nobody noticed.

Hmmm, I may have gone too far this time; I wrote the proposal before “Serving a higher purpose” was enacted, trying to avoid hypotheticals, but neglected to update it. You make good points, though, and I’ll aim to do as you recommend.