You can read This Soviet World or Blackshirts and Reds, if you'd like. There have been numerous books on the subject. You can even check the Wikipedia page for Soviet Democracy, the bit from Pat Sloan is especially relevant.
I have, while working in the Soviet Union, participated in an election. I, too, had a right to vote, as I was a working member of the community, and nationality and citizenship are no bar to electoral rights. The procedure was extremely simple. A general meeting of all the workers in our organisation was called. by the trade union committee, candidates were discussed, and a vote was taken by show of hands. Anybody present had the right to propose a candidate, and the one who was elected was not personally a member of the Party. In considering the claims of the candidates their past activities were discussed, they themselves had to answer questions as to their qualifications, anybody could express an opinion, for or against them, and the basis of all the discussion was: What justification had the candidates to represent their comrades on the local Soviet?
Anyone can write about how they could voice ideas and vote on them but where the proof of anyone actually voicing and idea and there being voting on it?
Are you asking seriously? This happened countless times, you need only understand the Soviet system of Democracy to realize this. Hell, you can read a Wikipedia page on the subject if you wish. There's also the Soviet Archvies, anecodtes from travelers like Pat Sloan, diaries, journals, newspaper articles, and so forth, though most are in Russian and never translated.
I feel like you're the one moving the goalposts. Remember, this is what you said.
Banning of factionalism was done when there were literal fascists and Capitalists trying to infiltrate the party and reinstate Tsarism for their profits. You were allowed to have different ifeas, voice them, and vote on them.
You say they banned certain ideologies, but beyond that you don't mention anything about elections or politics. You said people could voice different ideas and vote on them. You have not given actual evidence of that.