I think tagging tasks with Browser-Support at all is a wasted effort. We should've dropped this like we dropped the other fields from BugZilla (and imported as plain text in the description).

I guess at least the Web-Team-Backlog team will find these browser specific tags useful, and I have also seen many VisualEditor bugs being specific to i.e. Firefox.

A rename might help using them for the purpose they were created. For instance, what about #Opera-Specific, #Firefox-Specific...

There are 15 open tasks with the Opera project tag set so should not be too hard to (re)triage.
Do you really also care about closed ones, or about Opera 12 bugs? (Basically: Is this information of any real value or are we just categorizing for the sake of categorizing.)

In T76302#795501, @Krinkle wrote:

We should've dropped this

Your "we" is not the "we" of those folks who had and have a strong opinion that no information should ever be lost when migrating. In any case we could still always archive projects in Phab if we wanted.

In T76302#795544, @Qgil wrote:

I guess at least the Web-Team-Backlog team will find these browser specific tags useful

At least when it came to the "Mobile Platform" field in Bugzilla, it was set zero times in the last 12 months by a mobile team. I can imagine that the absolute number isn't too different for the "Web browser" field though I haven't checked.

A rename might help using them for the purpose they were created. For instance, what about #Opera-Specific, #Firefox-Specific...

That would have been a really good idea for Bugzilla where the "Web browser" field had a bug exposure. Now it's rather hidden as yet another project but I think I'd still go for #Opera-Browser-Specific etc.

In T76302#795544, @Qgil wrote:

I guess at least the Web-Team-Backlog team will find these browser specific tags useful, and I have also seen many VisualEditor bugs being specific to i.e. Firefox.

I'm not questioning the usefulness of a bug report detailing its relation to a specific browser. I'm questioning the use in maintaining tags for them. What would be the added value over simply stating it in the title or description (like we do for the other aspects of a bug, e.g. the page, class, country, user group etc.). Sure it matters, but every other aspect of a task name/description matters too. Is it useful to add tags? Have we used these for queries in the past?

In T76302#796188, @Aklapper wrote:

In T76302#795501, @Krinkle wrote:

We should've dropped this

(..) no information should ever be lost when migrating. (..)

They could've been converted the same way we did "Severity", "Version" and "See also". Simply appended to the bug report (which probably mentions it already in the description and/or title).

@Aklapper, @Krinkle, After reading your comments, I have no strong argument myself to keep/archive these browser tags.