As others have said, it's fine, as long as you're not using it to ban evade or otherwise break instance or community rules.

Also, come to think of it, even if it were okay, would it even be possible to have to be logged into two separate accounts on the same instance at the same time with the same browser profile? :/

Yep. But you need to use an alternative front end or a 3rd party app for that. If you try alx.lemmy.blahaj.zone for example, that's our Alexandrite front end, and you can have two or more accounts signed in with Alexandrite

I feel like it's fine. Think of it like Reddit in that regard. Lots of people have secondary accounts for different types of content. A lot of the time it's NSFW stuff but the same could be said for memes, politics, and personal stuff.

I think you would need to use either browser based profiles depending on which browser you use or a different frontend. If you are on mobile lots of apps can facilitate multiple accounts.

Na. Multiple accounts is fine as long as you don't vote manipulate.

It's also a good idea if you run communities. One account as your daily driver and the other for administrative actions.

I normally say in the application text that it is a second account and for what purpose I'm going to use it. If it isn't fine, then you'll know it when the request is rejected.

I generally think that’s fine as long as you aren’t using your accounts to break rules or avoid limits.