I've heard they're not just vectors but also have pores and loops in their root system in which some nematodes get stuck and digested.
That information is anecdotal though.
Oxalis, and a local weed that seems to spread its wild oats with the proclivity of a drunken sailor on shore leave after a 6 month deployment under the north pole.
Like many others, I am constantly battling Oxalis. The stuff @PaulH said about it being a vector for nematodes is news to me. Just another reason to hate Oxalis, I guess. I thought nematodes were mostly a problem if you have poor draining soil with low oxygen conditions. Hopefully, it's not as likely to be an issue with inorganic (APL) soil.