I think it depends what you use, i know for certain if you use shortkeys and are only using it to spam names for a runescape war in pvp/clw etc, even if you get muted they'l remove it if the names posted in clan leader forums section, happened to tons of people in my old clan and they all got un muted.
If however its for spamming in w2 etc longest i've seen for it was 12 day mute, never heard of anyone being banned for it, but i guess it'l depends on who handles your report and how many black marks you've got, i wouldn't suggest doing it either way.