The first two points are of course special, but I don't see a problem with the third one. If a language is written phonetically and does not use double glyphs to express different sounds, there will be no sequential glyph repetition.
For example in Spanish, this is rare. It usually occurs in r-rr and L-LL. The double letters express a different single sound. This is a spelling convention and is not strictly required.
For example in Spanish, this is rare. It usually occurs in r-rr and L-LL. The double letters express a different single sound. This is a spelling convention and is not strictly required.