By right - as long as you don't use both accounts to vote, it should be fine.
There's three different things to consider - the user as an individual, the user as the account, and the spirit of what the rules are.
With things like suspensions and question/answer bans - its an explicit sign that despite having the ability to perform certain actions, for the period, you're not trusted to do so. In these situations the individual is not trusted, and the use of account circumvents restrictions.
With the moderator binding-closures, and to a lesser extent, the gold dupe-hammers, its a sign one has significantly more trust.
With an alternate account, done ethically, you've spent the effort to gain the trust on that account where you can get the closevote. I'd argue you've earned the right on that account to do a non binding close, and as an individual, you have not lost that trust
The spirit of the sock puppet rules, as we have them have always meant to be to prevent fraud. In use most alternate accounts do allow for users to test things as lower rep, have a separate 'service' or 'bot' account, or seperate their work and personal accounts.
Suggested edits are trickier - but you'd be able to do so anonymously, and its a common way for a chatbot to get reputation. I think for most part the community is ok with it.
Practically, the situations where you absolutely need a non-binding close vote get less over time, you either get the community to do it, or just figure you need to do eventually. Getting the 3k reputation itself is trivial (I have about 900 rep on my alt account, after giving away about 1.2k rep) - just that on most sites it doesn't matter as much.