merge [gnu-screen] and [screen]
screen does seem too generic. I'm merging screen into gnu-screen. I did see a few questions under that tag that weren't about GNU screen, but apparently about the user's physical display. Any such ...
Merge the tags about Linear Tape Open: lto, lto-3, lto-4
I disagree. There are enough differences between LTO generations to warrant different tags. With the same argument, you could merge all Windows server variant tags into one.
Merge mod-pagespeed and page-speed or change tooltip
No, they shouldn't. mod_pagespeed concerns this, while page-speed is a much more generic term (see this question as an example). Those tags are not optimal, but they are not synonyms.
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