What you are doing is copying data bits from one tree-person to your tree-person,
This is not the same as actually merging two individuals into one -- which would result in linking 2 different trees (and the other tree owner might not be happy about the result). Ancestry.com has page designers to whom they evidently do not supply dictionaries. They use similarly confused terminology concerning saving citations for and data from database items to tree individuals - they call it "merging".
Then there was the web page earlier this year, advertising for an Ancestry.com project manager, who would be "Principal" in the area. The web page also said the hiree would be "Principle". The two words were only a couple of lines apart in the page.
Clearing hints can be tedious. If you have not done this before, go to your tree's List of People and click on the tab for Hints. Note that they are sorted by type. If you want to clear all the hints from trees, click on the bottom line and a list of each tree hint will appear. You can then click to 'ignore' each one without having to look at it. You can do the same with each hint type.
There used to be a link to "hint preferences" from the green leaf you'd see at the top of each Ancestry.com page after you log in. Hint Preferences has been moved to "Site Preferences" for which there is a link in a drop-down under your username after you have logged in. All you really can do is specify not to get hints from trees.