Too bad this suggestion was met with such opposition. :P My thinking behind it was that because spenseweed offers a potentially infinite source of hp recovery, it devalues the healing skill and natural regeneration of your PC. Even regeneration granting items have a downside in that they take up an inventory slot (and are a rare lategame find). Spense just encourages you to scum a large amount of it, equip it in the tool slot and spam 'u' every time you need to heal a few hp. There's no downsides, other than the extra weight you have to carry. I see it as kind of similar to other scummy (and already fixed) tactics such as the gremlin bomb. Gremlins = infinite stream of loot, so your actual luck with the RNG loses its meaning. Spense = infinite healing source with no downsides. Even though all players didn't abuse the gremlin trick, it still was fixed. Why not also make the herb less scummy, then?
Spense should be like a drug. With prolonged use it starts to lose its effect. You would have to be smarter about when to use it.
On a sidenote, I like SinsI's idea too.