Depends on a few things. If someone took the time to reply to my comment or post, they get an upvote as long as they’re not being a jerk, even if they disagree with me.
If it’s a post or comment in a post in a smaller community I upvote to show appreciation for their participation.
Funny / clever comments get an upvote.
I only downvote if they’re being a jerk. Disagreement does not warrant a downvote from me, if they are being civil about it.
As for tipping culture being built in to Lemmy, or in general, hell no - downvote for even mentioning that. /s