Unfortunately despite the impression given by the many poor explanations available (including the one you quoted), homologous is not a synonym for similar.
Homology is defined as the existence of shared ancestry1,2. Thus, structures being homologous simply means they had a common ancestor — i.e. homology is a relationship not a property of an individual structure.
The "definition" you quote is actually a description of what you typically see when comparing two homologous chromosomes within a species. High levels of sequence similarity suggest homology, but are not sufficient to prove it. (To test that requires building phylogenetic trees.)
(One classic example of this is the superficial similarity between dolphins and sharks, which is an example of convergence not homology. Another is the homology between bird and bat wings — they are not homologous as wings, though they are homologous as tetrapod forelimbs.)
Consequently, for two chromosomes to be homologous they must have descended from a (potentially much earlier) chromosome that has been duplicated possibly for many generations (the ancestral chromosome might even have existed in a now extinct ancestral species).
So, if an inversion happens within a chromosome (and changes the ordering of the genetic loci) that chromosome is still homologous to the parental type chromosome that didn't undergo inversion.
ETA: Note that chromosomes don't need to be in the same cell (or even the same species) to be homologous and chromosomes can be homologous even if the cell they are in is not diploid. For example, the human chromosome 1 is homologous to the chimpanzee chromosome 1.
Similarity is a measurement of "distance" between sequences, but while very similar sequences are likely to be homologous there is no magical value of similarity that proves (or disproves) homology.
Individual humans are about 99.9% identical (depends on how you measure this) at the nucleotide level, so that will also be true for chromosome 1.
Finally, the UC Berkeley Museum of Paleontology also has useful resources for understanding evolution including some material on homology — e.g.:
1: Brigandt, Ingo, "Essay: Homology". Embryo Project Encyclopedia (2011-11-23). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/1754.
2: Mindell, D. P., & Meyer, A. (2001). Homology evolving. Trends in Ecology & Evolution, 16(8), 434-440.