I think la selpa'i has perfectly responded to the question, but I have an objection about the English interpretation of {ka}, and a complement to the explanation about relation of {ka} and other abstractors.
{mi nelci lo ka limna} means rather "I like property of swimmer", not "swimming". {ka} (property) signifies a special case of {si'o} (idea, concept) in Lojban.
Both {lo si'o broda} and {lo ka broda} signify « signified » (meaning) of predicate {broda}. The difference is that a sentence in {ka}-clause has only one sumti place blank (denoted with {ce'u}), while a sentence in {si'o}-clause has all places blank. {si'o}-{ka}-{du'u} forms full set of predicate abstraction.
lo si'o (ce'u) limna (ce'u) :
idea, concept of swimming ; idea, concept that is signified by a predicate "X swims in fluid Y."
lo ka (ce'u) limna (zo'e) :
property of swimmer ; property that is signified by a predicate "X swims in some fluid," "X has property of swimmer in some fluid."
lo ka (zo'e) limna ce'u :
property of swimming fluid ; property that is signified by a predicate "someone swims in fluid Y," "Y has property of fluid in which someone swims."
lo du'u (zo'e) limna (zo'e) :
« signified » of a predicate "someone swims in some fluid."
lo se du'u (zo'e) limna (zo'e) :
« signifying » (string of symbols) of a predicate "someone swims in some fluid."