Invisible character treated as word?

[David Epstein]

For a tab-delimited table of numbers, I want to be sure that none of the numbers is surrounded by invisible spaces that will interfere with using the numbers in calculation.  I do that by overwriting each cell with "word 1 to -1 of" that cell.
This generally works fine, but was tripped up by a case in which a number was followed by what looked like two spaces.  Closer inspection revealed that the second space had charToNum value 202.  Even though it is invisible, LiveCode (5.5) seems to treat it as a word, and so my script did not strip it out.
Are there other characters that are always or sometimes invisible that cause the same problem?  And what is a remedy?
Many thanks.

David Epstein