As a Czech, Interslavic feels to me like a czech written by a dystrophic person. It's really natural.
EDIT: Not "dystrophic" but "dysgraphic".
Dystrophic? (As in: affected by tissue degeneration?)
Oh, no. A typo. I meant "dysgraphic". Someone affected by issues with writing)
To give a second opinion of a Czech person, it doesn't look anything like Czech text to me. If I had to guess, I would say Serbo-Croatian or Slovenian (probably because of the orthography).