Limits I think would be reasonable to impose on a PF listing's minimum IL:
  • PF required IL cannot be higher than party leader's IL
  • PF required IL cannot be higher than the maximum currently attainable IL

Requiring a minimum IL higher than you yourself have is probably rude.
Requiring a minimum IL higher than anyone can attain means you obviously don't want the party to fill and drop from the listings, so it is some sort of advertisement. There are legitimate uses for this, e.g., inviting the whole DC to your FC's holiday party or a tasteful memorial; however, it seems like these are far rarer than people advertising for illegitimate things.