I understand.

I feel the emphasis should be on the hiding of one's motives, though, not on being seen as universally amiable. In Emma, Jane Fairfax is disliked by Emma because of her reserve. That applies much more so than the generally agreeable social facade. Let us rewrite Anne and Lady Russell's dialogue in that fashion:

[Anne exclaims,] "And then, [his] reserve! I never could attach myself to any one so completely reserved."

"It is a most repulsive quality, indeed," said [Lady Russell]. (In my rewrite, Lady Russell allows Anne to say no, you will note!) "Oftentimes very convenient, no doubt, but never pleasing. There is safety in reserve, but no attraction. One cannot love a reserved person."