Someone else's post in a forum is hardly proof, but in this case, you are correct. Swordtails and Platies can cross. Mollies, Endlers, and Guppies can cross as well.
very true infact there was a case on here not too long ago where someone bred a male molly to a female guppy which resulted in fry, although they didn't live long
thats weird they dont look anything a like.