These are points where there is no consensus yet.

Adjacent vowels. What should be the restrictions?

For gismu and lujvo there is no discussion. For cmene, cmavo and fu'ivla, there are different options:

Restrictive option

ai, au, ei, oi allowed always.
ia, ie, ii, io, iu, ua, ue, ui, uo, uu only at the beginning of a cmavo, cmene or fu'ivla.
No vowel triples allowed.
y not allowed next to a vowel.

Permissive option

Any string of vowels allowed always. Syllables break in pairs from left to right for ai, au, ei, oi, ia, ie, ii, io, iu, ua, ue, ui, uo, uu, otherwise a single vowel forms a syllable. iy and iy allowed in cmene and cmavo.

(This is the option currently implemented.)

Other options

. . .

Rafsi fu'ivla

Currently we allow any fu'ivla as final rafsi, and all those that can be non-final are allowed in non-final position. Fuhivla starting with vowel that can otherwise have a rafsi are allowed as initial rafsi.

Hyphens

CVC-y-

Currently the y-hyphen is allowed after any CVC-rafsi. Officially it is allowed only when it is required (i.e. between an impermissible pair or to correct a tosmabru failure).
RATIONALE: If one gets used to a lujvo like tosymabru, it is nice to be able to produce further formations like {naltosymabru} without having to remember to remove the hyphen in this case.

CVV-r/n-

Currently this is allowed only when it is required as the official rule says. However, it would not be a bad idea to allow it in any position.
RATIONALE: same as for the y-hyphen. If one gets used to the lujvo {li'erla'i}, it is a pain to remember that {nalyli'erla'i} is not a lujvo and one should use {nalyliela'i} instead. Allowing the hyphen always takes a little space away from fu'ivla, but makes things easier for the user.