Yes, the overhelpful posting software has decided to get lazy about this one thing: at-mentions have become literalists. I could tag Áine if I wanted to because my fingers know the alt-number combo for capital Á. (My brain has to pay attention to my fingers: it's 0193.) Typing "@Aine" no longer works to bring up her username. (I can also get the accented letters by switching keyboard layouts to Hungarian, but I never remember where the "at" sign is on that.) (I'm sure @Gordon Collett can tell us the fruity equivalents for generating Á.)

Ah! But at-mentioning is apparently not case-sensitive. Typing shift-2 followed by alt-0225 would also work to "summon" Áine. Thank goodness for small mercies.

Oh: the "at" sign must be at the beginning of the line or follow a space. If you click to add an at-mention somewhere and get the cursor location off by one, or if you try to put it in quotation marks, it will not work.

(@Paul W, alt-number combos only work with the numeric keypad, not with the numbers across the top.)

I cannot get it to replicate your screenshot on my end. "@Á" just gets Áine.

"@A" gets five apparently-random users starting with A. (The five names are in alphanumeric order, but there are a lot more than two usernames beginning with "Ab" in this Community.)

Typing as far as "@Aine" gets four users, none of them Áine.

@ by itself generates the three users who apparently have the "at" sign as the first character of their usernames.

I can find no rhyme or reason in which five users show up in the drop-down. "@Juli" has me second on the list.

Typing one character further, however, removes me from the drop-down.

I wonder if the problem is that the old algorithm still occasionally "holds sway", but only in some weird set of circumstances?